diff --git a/src/doc/rustc/src/exploit-mitigations.md b/src/doc/rustc/src/exploit-mitigations.md index 172048704f48d..d4e2fc52e973f 100644 --- a/src/doc/rustc/src/exploit-mitigations.md +++ b/src/doc/rustc/src/exploit-mitigations.md @@ -1,12 +1,12 @@ # Exploit Mitigations -This chapter documents the exploit mitigations supported by the Rust -compiler, and is by no means an extensive survey of the Rust programming -language’s security features. +This chapter documents the exploit mitigations supported by the Rust compiler, +and is by no means an extensive survey of the Rust programming language’s +security features. This chapter is for software engineers working with the Rust programming -language, and assumes prior knowledge of the Rust programming language and -its toolchain. +language, and assumes prior knowledge of the Rust programming language and its +toolchain. ## Introduction @@ -14,8 +14,8 @@ its toolchain. The Rust programming language provides memory[1] and thread[2] safety guarantees via its ownership[3], references and borrowing[4], and slice types[5] features. However, Unsafe Rust[6] introduces unsafe blocks, unsafe -functions and methods, unsafe traits, and new types that are not subject to -the borrowing rules. +functions and methods, unsafe traits, and new types that are not subject to the +borrowing rules. Parts of the Rust standard library are implemented as safe abstractions over unsafe code (and historically have been vulnerable to memory corruption[7]). @@ -23,33 +23,32 @@ Furthermore, the Rust code and documentation encourage creating safe abstractions over unsafe code. This can cause a false sense of security if unsafe code is not properly reviewed and tested. -Unsafe Rust introduces features that do not provide the same memory and -thread safety guarantees. This causes programs or libraries to be -susceptible to memory corruption (CWE-119)[8] and concurrency issues -(CWE-557)[9]. Modern C and C++ compilers provide exploit mitigations to -increase the difficulty to exploit vulnerabilities resulting from these -issues. Therefore, the Rust compiler must also support these exploit -mitigations in order to mitigate vulnerabilities resulting from the use of -Unsafe Rust. This chapter documents these exploit mitigations and how they -apply to Rust. +Unsafe Rust introduces features that do not provide the same memory and thread +safety guarantees. This causes programs or libraries to be susceptible to +memory corruption (CWE-119)[8] and concurrency issues (CWE-557)[9]. Modern C +and C++ compilers provide exploit mitigations to increase the difficulty to +exploit vulnerabilities resulting from these issues. Therefore, the Rust +compiler must also support these exploit mitigations in order to mitigate +vulnerabilities resulting from the use of Unsafe Rust. This chapter documents +these exploit mitigations and how they apply to Rust. -This chapter does not discuss the effectiveness of these exploit mitigations -as they vary greatly depending on several factors besides their design and -implementation, but rather describe what they do, so their effectiveness can -be understood within a given context. +This chapter does not discuss the effectiveness of these exploit mitigations as +they vary greatly depending on several factors besides their design and +implementation, but rather describe what they do, so their effectiveness can be +understood within a given context. ## Exploit mitigations -This section documents the exploit mitigations applicable to the Rust -compiler when building programs for the Linux operating system on the AMD64 -architecture and equivalent.1 +This section documents the exploit mitigations applicable to the Rust compiler +when building programs for the Linux operating system on the AMD64 architecture +and equivalent.1 All examples in this section were built using +nightly builds of the Rust compiler on Debian testing. -The Rust Programming Language currently has no specification. The Rust -compiler (i.e., rustc) is the language reference implementation. All -references to “the Rust compiler” in this chapter refer to the language -reference implementation. +The Rust Programming Language currently has no specification. The Rust compiler +(i.e., rustc) is the language reference implementation. All references to “the +Rust compiler” in this chapter refer to the language reference implementation. Table I \ Summary of exploit mitigations supported by the Rust compiler when building @@ -83,8 +82,8 @@ instructing the dynamic linker to load it similarly to a shared object at a random load address, thus also benefiting from address-space layout randomization (ASLR). This is also referred to as “full ASLR”. -The Rust compiler supports position-independent executable, and enables it -by default since version 0.12.0 (2014-10-09)[10]–[13]. +The Rust compiler supports position-independent executable, and enables it by +default since version 0.12.0 (2014-10-09)[10]–[13]. ```text $ readelf -h target/release/hello-rust | grep Type: @@ -93,8 +92,7 @@ $ readelf -h target/release/hello-rust | grep Type: Fig. 1. Checking if an executable is a position-independent executable. An executable with an object type of `ET_DYN` (i.e., shared object) and not -`ET_EXEC` (i.e., executable) is a position-independent executable (see Fig. -1). +`ET_EXEC` (i.e., executable) is a position-independent executable (see Fig. 1). ### Integer overflow checks @@ -104,8 +102,11 @@ behavior (which may cause vulnerabilities) by checking for results of signed and unsigned integer computations that cannot be represented in their type, resulting in an overflow or wraparound. -The Rust compiler supports integer overflow checks, and enables it when -debug assertions are enabled since version 1.1.0 (2015-06-25)[14]–[20]. +The Rust compiler supports integer overflow checks, and enables it when debug +assertions are enabled since version 1.0.0 (2015-05-15)[14]–[17], but support +for it was not completed until version 1.1.0 (2015-06-25)[16]. An option to +control integer overflow checks was later stabilized in version 1.17.0 +(2017-04-27)[18]–[20]. ```compile_fail fn main() { @@ -136,21 +137,21 @@ u: 0 Fig. 4. Build and execution of hello-rust-integer with debug assertions disabled. -Integer overflow checks are enabled when debug assertions are enabled (see -Fig. 3), and disabled when debug assertions are disabled (see Fig. 4). To -enable integer overflow checks independently, use the option to control -integer overflow checks, scoped attributes, or explicit checking methods -such as `checked_add`2. -It is recommended that explicit wrapping methods such as `wrapping_add` be -used when wrapping semantics are intended, and that explicit checking and -wrapping methods always be used when using Unsafe Rust. +It is recommended that explicit wrapping methods such as `wrapping_add` be used +when wrapping semantics are intended, and that explicit checking and wrapping +methods always be used when using Unsafe Rust. -2\. See [the `u32` docs](../std/primitive.u32.html) -for more information on the checked, overflowing, saturating, and wrapping -methods (using u32 as an example). ↩ +2\. See [the `u32` docs](../std/primitive.u32.html) for more +information on the checked, overflowing, saturating, and wrapping methods +(using u32 as an example). ↩ ### Non-executable memory regions @@ -158,17 +159,16 @@ class="reversefootnote" role="doc-backlink">↩ Non-executable memory regions increase the difficulty of exploitation by limiting the memory regions that can be used to execute arbitrary code. Most modern processors provide support for the operating system to mark memory -regions as non executable, but it was previously emulated by software, such -as in grsecurity/PaX's -[PAGEEXEC](https://pax.grsecurity.net/docs/pageexec.txt) and -[SEGMEXEC](https://pax.grsecurity.net/docs/segmexec.txt), on processors that -did not provide support for it. This is also known as “No Execute (NX) Bit”, -“Execute Disable (XD) Bit”, “Execute Never (XN) Bit”, and others. +regions as non executable, but it was previously emulated by software, such as +in grsecurity/PaX’s [PAGEEXEC](https://pax.grsecurity.net/docs/pageexec.txt) +and [SEGMEXEC](https://pax.grsecurity.net/docs/segmexec.txt), on processors +that did not provide support for it. This is also known as “No Execute (NX) +Bit”, “Execute Disable (XD) Bit”, “Execute Never (XN) Bit”, and others. The Rust compiler supports non-executable memory regions, and enables it by -default since its initial release, version 0.1 (2012-01-20)[21], [22], but -has regressed since then[23]–[25], and enforced by default since version -1.8.0 (2016-04-14)[25]. +default since its initial release, version 0.1 (2012-01-20)[21], [22], but has +regressed since then[23]–[25], and enforced by default since version 1.8.0 +(2016-04-14)[25]. ```text $ readelf -l target/release/hello-rust | grep -A 1 GNU_STACK @@ -178,9 +178,9 @@ $ readelf -l target/release/hello-rust | grep -A 1 GNU_STACK Fig. 5. Checking if non-executable memory regions are enabled for a given binary. -The presence of an element of type `PT_GNU_STACK` in the program header -table with the `PF_X` (i.e., executable) flag unset indicates non-executable -memory regions3 are enabled for a given binary (see Fig. 5). Conversely, the presence of an element of type `PT_GNU_STACK` in the program header table with the `PF_X` flag set or the absence of an element of type @@ -196,38 +196,40 @@ class="reversefootnote" role="doc-backlink">↩ Stack clashing protection protects the stack from overlapping with another memory region—allowing arbitrary data in both to be overwritten using each -other—by reading from the stack pages as the stack grows to cause a page -fault when attempting to read from the guard page/region. This is also -referred to as “stack probes” or “stack probing”. +other—by reading from the stack pages as the stack grows to cause a page fault +when attempting to read from the guard page/region. This is also referred to as +“stack probes” or “stack probing”. The Rust compiler supports stack clashing protection via stack probing, and enables it by default since version 1.20.0 (2017-08-31)[26]–[29]. -![Screenshot of IDA Pro listing cross references to __rust_probestack in hello-rust.](images/image1.png "Cross references to __rust_probestack in hello-rust.") -Fig. 6. IDA Pro listing cross references to `__rust_probestack` in -hello-rust. - ```rust -fn hello() { - println!("Hello, world!"); +fn main() { + let v: [u8; 16384] = [1; 16384]; + let first = &v[0]; + println!("The first element is: {first}"); } +``` +Fig. 6. hello-rust-stack-probe-1 program. +![Screenshot of IDA Pro listing the "unrolled loop" stack probe variant in modified hello-rust.](images/image1.png "The \"unrolled loop\" stack probe variant in modified hello-rust.") +Fig. 7. The "unrolled loop" stack probe variant in modified hello-rust. + +```rust fn main() { - let _: [u64; 1024] = [0; 1024]; - hello(); + let v: [u8; 65536] = [1; 65536]; + let first = &v[0]; + println!("The first element is: {first}"); } ``` -Fig 7. Modified hello-rust. +Fig. 8. hello-rust-stack-probe-2 program. -![Screenshot of IDA Pro listing cross references to __rust_probestack in modified hello-rust.](images/image2.png "Cross references to __rust_probestack in modified hello-rust.") -Fig. 8. IDA Pro listing cross references to `__rust_probestack` in modified -hello-rust. +![Screenshot of IDA Pro listing the "standard loop" stack probe variant in modified hello-rust.](images/image2.png "The \"standard loop\" stack probe variant in modified hello-rust.") +Fig. 9. The "standard loop" stack probe variant in modified hello-rust. -To check if stack clashing protection is enabled for a given binary, search -for cross references to `__rust_probestack`. The `__rust_probestack` is -called in the prologue of functions whose stack size is larger than a page -size (see Fig. 6), and can be forced for illustration purposes by modifying -the hello-rust example as seen in Fig. 7 and Fig. 8. +To check if stack clashing protection is enabled for a given binary, look for +any of the two stack probe variants in the prologue of functions whose stack +size is larger than a page size (see Figs. 6–9). ### Read-only relocations and immediate binding @@ -246,21 +248,20 @@ $ readelf -l target/release/hello-rust | grep GNU_RELRO ``` Fig. 9. Checking if read-only relocations is enabled for a given binary. -The presence of an element of type `PT_GNU_RELRO` in the program header -table indicates read-only relocations are enabled for a given binary (see -Fig. 9). Conversely, the absence of an element of type `PT_GNU_RELRO` in the -program header table indicates read-only relocations are not enabled for a -given binary. +The presence of an element of type `PT_GNU_RELRO` in the program header table +indicates read-only relocations are enabled for a given binary (see Fig. 9). +Conversely, the absence of an element of type `PT_GNU_RELRO` in the program +header table indicates read-only relocations are not enabled for a given +binary. **Immediate binding** protects additional segments containing relocations -(i.e., `.got.plt`) from being overwritten by instructing the dynamic linker -to perform all relocations before transferring control to the program during -startup, so all segments containing relocations can be marked read only -(when combined with read-only relocations). This is also referred to as -“full RELRO”. +(i.e., `.got.plt`) from being overwritten by instructing the dynamic linker to +perform all relocations before transferring control to the program during +startup, so all segments containing relocations can be marked read only (when +combined with read-only relocations). This is also referred to as “full RELRO”. -The Rust compiler supports immediate binding, and enables it by default -since version 1.21.0 (2017-10-12)[30], [31]. +The Rust compiler supports immediate binding, and enables it by default since +version 1.21.0 (2017-10-12)[30], [31]. ```text $ readelf -d target/release/hello-rust | grep BIND_NOW @@ -270,16 +271,15 @@ Fig. 10. Checking if immediate binding is enabled for a given binary. The presence of an element with the `DT_BIND_NOW` tag and the `DF_BIND_NOW` flag4 in the dynamic section indicates immediate -binding is enabled for a given binary (see Fig. 10). Conversely, the absence -of an element with the `DT_BIND_NOW` tag and the `DF_BIND_NOW` flag in the -dynamic section indicates immediate binding is not enabled for a given -binary. +class="footnote">4 in the dynamic section indicates immediate binding +is enabled for a given binary (see Fig. 10). Conversely, the absence of an +element with the `DT_BIND_NOW` tag and the `DF_BIND_NOW` flag in the dynamic +section indicates immediate binding is not enabled for a given binary. The presence of both an element of type `PT_GNU_RELRO` in the program header -table and of an element with the `DT_BIND_NOW` tag and the `DF_BIND_NOW` -flag in the dynamic section indicates full RELRO is enabled for a given -binary (see Fig. 9 and Fig. 10). +table and of an element with the `DT_BIND_NOW` tag and the `DF_BIND_NOW` flag +in the dynamic section indicates full RELRO is enabled for a given binary (see +Figs. 9–10). 4\. And the `DF_1_NOW` flag for some link editors. ↩ @@ -287,26 +287,24 @@ href="#fnref:4" class="reversefootnote" role="doc-backlink">↩ ### Heap corruption protection -Heap corruption protection protects memory allocated dynamically by -performing several checks, such as checks for corrupted links between list -elements, invalid pointers, invalid sizes, double/multiple “frees” of the -same memory allocated, and many corner cases of these. These checks are -implementation specific, and vary per allocator. +Heap corruption protection protects memory allocated dynamically by performing +several checks, such as checks for corrupted links between list elements, +invalid pointers, invalid sizes, double/multiple “frees” of the same memory +allocated, and many corner cases of these. These checks are implementation +specific, and vary per allocator. [ARM Memory Tagging Extension (MTE)](https://community.arm.com/developer/ip-products/processors/b/processors-ip-blog/posts/enhancing-memory-safety), -when available, will provide hardware assistance for a probabilistic -mitigation to detect memory safety violations by tagging memory allocations, -and automatically checking that the correct tag is used on every memory -access. +when available, will provide hardware assistance for a probabilistic mitigation +to detect memory safety violations by tagging memory allocations, and +automatically checking that the correct tag is used on every memory access. Rust’s default allocator has historically been -[jemalloc](http://jemalloc.net/), and it has long been the cause of issues -and the subject of much discussion[32]–[38]. Consequently, it has been -removed as the default allocator in favor of the operating system’s standard -C library default allocator5 since version 1.32.0 -(2019-01-17)[39]. +[jemalloc](http://jemalloc.net/), and it has long been the cause of issues and +the subject of much discussion[32]–[38]. Consequently, it has been removed as +the default allocator in favor of the operating system’s standard C library +default allocator5 since version 1.32.0 (2019-01-17)[39]. ```rust,no_run fn main() { @@ -330,8 +328,7 @@ $ cargo run free(): invalid next size (normal) Aborted ``` -Fig. 12. Build and execution of hello-rust-heap with debug assertions -enabled. +Fig. 12. Build and execution of hello-rust-heap with debug assertions enabled. ```text $ cargo run --release @@ -341,47 +338,41 @@ $ cargo run --release free(): invalid next size (normal) Aborted ``` -Fig. 13. Build and execution of hello-rust-heap with debug assertions -disabled. +Fig. 13. Build and execution of hello-rust-heap with debug assertions disabled. -Heap corruption checks are being performed when using the default allocator -(i.e., the GNU Allocator) as seen in Fig. 12 and Fig. 13. +Heap corruption checks are performed when using the default allocator (i.e., +the GNU Allocator) (see Figs. 12–13). 5\. Linux's standard C library default allocator is the GNU -Allocator, which is derived from ptmalloc (pthreads malloc) by Wolfram -Gloger, which in turn is derived from dlmalloc (Doug Lea malloc) by Doug -Lea. ↩ +Allocator, which is derived from ptmalloc (pthreads malloc) by Wolfram Gloger, +which in turn is derived from dlmalloc (Doug Lea malloc) by Doug Lea. ↩ ### Stack smashing protection -Stack smashing protection protects programs from stack-based buffer -overflows by inserting a random guard value between local variables and the -saved return instruction pointer, and checking if this value has changed -when returning from a function. This is also known as “Stack Protector” or -“Stack Smashing Protector (SSP)”. +Stack smashing protection protects programs from stack-based buffer overflows +by inserting a random guard value between local variables and the saved return +instruction pointer, and checking if this value has changed when returning from +a function. This is also known as “Stack Protector” or “Stack Smashing +Protector (SSP)”. -The Rust compiler supports stack smashing protection on nightly builds[42]. +The Rust compiler supports stack smashing protection on nightly builds[40]. ![Screenshot of IDA Pro listing cross references to __stack_chk_fail in hello-rust.](images/image3.png "Cross references to __stack_chk_fail in hello-rust.") -Fig. 14. IDA Pro listing cross references to `__stack_chk_fail` in -hello-rust. +Fig. 14. IDA Pro listing cross references to `__stack_chk_fail` in hello-rust. -To check if stack smashing protection is enabled for a given binary, search -for cross references to `__stack_chk_fail`. The presence of these -cross-references in Rust-compiled code (e.g., `hello_rust::main`) indicates -that the stack smashing protection is enabled (see Fig. 14). +To check if stack smashing protection is enabled for a given binary, search for +cross references to `__stack_chk_fail` (see Fig. 14). ### Forward-edge control flow protection -Forward-edge control flow protection protects programs from having its -control flow changed/hijacked by performing checks to ensure that -destinations of indirect branches are one of their valid destinations in the -control flow graph. The comprehensiveness of these checks vary per -implementation. This is also known as “forward-edge control flow integrity -(CFI)”. +Forward-edge control flow protection protects programs from having its control +flow changed/hijacked by performing checks to ensure that destinations of +indirect branches are one of their valid destinations in the control flow +graph. The comprehensiveness of these checks vary per implementation. This is +also known as “forward-edge control flow integrity (CFI)”. Newer processors provide hardware assistance for forward-edge control flow protection, such as ARM Branch Target Identification (BTI), ARM Pointer @@ -394,22 +385,19 @@ commercially available [grsecurity/PaX Reuse Attack Protector (RAP)](https://grsecurity.net/rap_faq). The Rust compiler supports forward-edge control flow protection on nightly -builds[40]-[41] 6. ```text -$ readelf -s -W target/debug/rust-cfi | grep "\.cfi" - 12: 0000000000005170 46 FUNC LOCAL DEFAULT 14 _RNvCsjaOHoaNjor6_8rust_cfi7add_one.cfi - 15: 00000000000051a0 16 FUNC LOCAL DEFAULT 14 _RNvCsjaOHoaNjor6_8rust_cfi7add_two.cfi - 17: 0000000000005270 396 FUNC LOCAL DEFAULT 14 _RNvCsjaOHoaNjor6_8rust_cfi4main.cfi -... +$ readelf -s -W target/release/hello-rust | grep "\.cfi" + 5: 0000000000006480 657 FUNC LOCAL DEFAULT 15 _ZN10hello_rust4main17h4e359f1dcd627c83E.cfi ``` -Fig. 15. Checking if LLVM CFI is enabled for a given binary[41]. +Fig. 15. Checking if LLVM CFI is enabled for a given binary. The presence of symbols suffixed with ".cfi" or the `__cfi_init` symbol (and -references to `__cfi_check`) indicates that LLVM CFI (i.e., forward-edge control -flow protection) is enabled for a given binary. Conversely, the absence of -symbols suffixed with ".cfi" or the `__cfi_init` symbol (and references to +references to `__cfi_check`) indicates that LLVM CFI (i.e., forward-edge +control flow protection) is enabled for a given binary. Conversely, the absence +of symbols suffixed with ".cfi" or the `__cfi_init` symbol (and references to `__cfi_check`) indicates that LLVM CFI is not enabled for a given binary (see Fig. 15). @@ -421,48 +409,47 @@ class="reversefootnote" role="doc-backlink">↩ ### Backward-edge control flow protection **Shadow stack** protects saved return instruction pointers from being -overwritten by storing a copy of them on a separate (shadow) stack, and -using these copies as authoritative values when returning from functions. -This is also known as “ShadowCallStack” and “Return Flow Guard”, and is -considered an implementation of backward-edge control flow protection (or -“backward-edge CFI”). +overwritten by storing a copy of them on a separate (shadow) stack, and using +these copies as authoritative values when returning from functions. This is +also known as “ShadowCallStack” and “Return Flow Guard”, and is considered an +implementation of backward-edge control flow protection (or “backward-edge +CFI”). **Safe stack** protects not only the saved return instruction pointers, but -also register spills and some local variables from being overwritten by -storing unsafe variables, such as large arrays, on a separate (unsafe) -stack, and using these unsafe variables on the separate stack instead. This -is also known as “SafeStack”, and is also considered an implementation of -backward-edge control flow protection. +also register spills and some local variables from being overwritten by storing +unsafe variables, such as large arrays, on a separate (unsafe) stack, and using +these unsafe variables on the separate stack instead. This is also known as +“SafeStack”, and is also considered an implementation of backward-edge control +flow protection. -Both shadow and safe stack are intended to be a more comprehensive -alternatives to stack smashing protection as they protect the saved return -instruction pointers (and other data in the case of safe stack) from -arbitrary writes and non-linear out-of-bounds writes. +Both shadow and safe stack are intended to be a more comprehensive alternatives +to stack smashing protection as they protect the saved return instruction +pointers (and other data in the case of safe stack) from arbitrary writes and +non-linear out-of-bounds writes. Newer processors provide hardware assistance for backward-edge control flow -protection, such as ARM Pointer Authentication, and Intel Shadow Stack as -part of Intel CET. +protection, such as ARM Pointer Authentication, and Intel Shadow Stack as part +of Intel CET. -The Rust compiler supports shadow stack for aarch64 only -7 -on nightly Rust compilers [43]-[44]. Safe stack is available on nightly -Rust compilers [45]-[46]. +The Rust compiler supports shadow stack for the AArch64 architecture7on +nightly builds[43]-[44], and also supports safe stack on nightly +builds[45]-[46]. ```text $ readelf -s target/release/hello-rust | grep __safestack_init - 1177: 00000000000057b0 444 FUNC GLOBAL DEFAULT 9 __safestack_init + 678: 0000000000008c80 426 FUNC GLOBAL DEFAULT 15 __safestack_init ``` Fig. 16. Checking if LLVM SafeStack is enabled for a given binary. -The presence of the `__safestack_init` symbol indicates that LLVM SafeStack -is enabled for a given binary (see Fig. 16). Conversely, the absence of the -`__safestack_init` symbol indicates that LLVM SafeStack is not enabled for a -given binary. +The presence of the `__safestack_init` symbol indicates that LLVM SafeStack is +enabled for a given binary. Conversely, the absence of the `__safestack_init` +symbol indicates that LLVM SafeStack is not enabled for a given binary (see +Fig. 16). -7\. The shadow stack implementation for the AMD64 -architecture and equivalent in LLVM was removed due to performance and -security issues. ↩ +7\. The shadow stack implementation for the AMD64 architecture +and equivalent in LLVM was removed due to performance and security issues. ↩ ## Appendix @@ -470,29 +457,28 @@ role="doc-backlink">↩ As of the latest version of the [Linux Standard Base (LSB) Core Specification](https://refspecs.linuxfoundation.org/LSB_5.0.0/LSB-Core-generic/LSB-Core-generic/progheader.html), the `PT_GNU_STACK` program header indicates whether the stack should be -executable, and the absence of this header indicates that the stack should -be executable. However, the Linux kernel currently sets the -`READ_IMPLIES_EXEC` personality upon loading any executable with the -`PT_GNU_STACK` program header and the `PF_X `flag set or with the absence of -this header, resulting in not only the stack, but also all readable virtual -memory mappings being executable. +executable, and the absence of this header indicates that the stack should be +executable. However, the Linux kernel currently sets the `READ_IMPLIES_EXEC` +personality upon loading any executable with the `PT_GNU_STACK` program header +and the `PF_X` flag set or with the absence of this header, resulting in not +only the stack, but also all readable virtual memory mappings being executable. An attempt to fix this [was made in 2012](https://lore.kernel.org/lkml/f298f914-2239-44e4-8aa1-a51282e7fac0@zmail15.collab.prod.int.phx2.redhat.com/), and another [was made in 2020](https://lore.kernel.org/kernel-hardening/20200327064820.12602-1-keescook@chromium.org/). The former never landed, and the latter partially fixed it, but introduced -other issues—the absence of the `PT_GNU_STACK` program header still causes -not only the stack, but also all readable virtual memory mappings to be -executable in some architectures, such as IA-32 and equivalent (or causes -the stack to be non-executable in some architectures, such as AMD64 and -equivalent, contradicting the LSB). +other issues—the absence of the `PT_GNU_STACK` program header still causes not +only the stack, but also all readable virtual memory mappings to be executable +in some architectures, such as IA-32 and equivalent (or causes the stack to be +non-executable in some architectures, such as AMD64 and equivalent, +contradicting the LSB). -The `READ_IMPLIES_EXEC` personality needs to be completely separated from -the `PT_GNU_STACK` program header by having a separate option for it (or -setarch -X could just be used whenever `READ_IMPLIES_EXEC` is needed), and -the absence of the `PT_GNU_STACK` program header needs to have more secure -defaults (unrelated to `READ_IMPLIES_EXEC`). +The `READ_IMPLIES_EXEC` personality needs to be completely separated from the +`PT_GNU_STACK` program header by having a separate option for it (or setarch -X +could just be used whenever `READ_IMPLIES_EXEC` is needed), and the absence of +the `PT_GNU_STACK` program header needs to have more secure defaults (unrelated +to `READ_IMPLIES_EXEC`). ## References @@ -576,19 +562,19 @@ defaults (unrelated to `READ_IMPLIES_EXEC`). 25. A. Clark. “Explicitly disable stack execution on linux and bsd #30859.” GitHub. . -26. “Replace stack overflow checking with stack probes #16012.” GitHub. +26. Zoxc. “Replace stack overflow checking with stack probes #16012.” GitHub. . -27. B. Striegel. “Extend stack probe support to non-tier-1 platforms, and - clarify policy for mitigating LLVM-dependent unsafety #43241.” GitHub. - . - -28. A. Crichton. “rustc: Implement stack probes for x86 #42816.” GitHub. +27. A. Crichton. “rustc: Implement stack probes for x86 #42816.” GitHub. . -29. A. Crichton. “Add \_\_rust\_probestack intrinsic #175.” GitHub. +28. A. Crichton. “Add \_\_rust\_probestack intrinsic #175.” GitHub. . +29. S. Guelton, S. Ledru, J. Stone. “Bringing Stack Clash Protection to Clang / + X86 — the Open Source Way.” The LLVM Project Blog. + . + 30. B. Anderson. “Consider applying -Wl,-z,relro or -Wl,-z,relro,-z,now by default #29877.” GitHub. . @@ -621,16 +607,16 @@ defaults (unrelated to `READ_IMPLIES_EXEC`). 39. A. Crichton. “Remove the alloc\_jemalloc crate #55238.” GitHub. . -40. R. de C Valle. “Tracking Issue for LLVM Control Flow Integrity (CFI) Support +40. bbjornse. “Add codegen option for using LLVM stack smash protection #84197.” + GitHub. + +41. R. de C. Valle. “Tracking Issue for LLVM Control Flow Integrity (CFI) Support for Rust #89653.” GitHub. . -41. “ControlFlowIntegrity.” The Rust Unstable Book. +42. “ControlFlowIntegrity.” The Rust Unstable Book. [https://doc.rust-lang.org/unstable-book/compiler-flags/sanitizer.html#controlflowintegrity](../unstable-book/compiler-flags/sanitizer.html#controlflowintegrity). -42. bbjornse. “add codegen option for using LLVM stack smash protection #84197.” - GitHub. - -43. ivanloz. “Add support for LLVM ShadowCallStack. #98208.” GitHub. +43. I. Lozano. “Add support for LLVM ShadowCallStack #98208.” GitHub. . 44. “ShadowCallStack.” The Rust Unstable Book. diff --git a/src/doc/rustc/src/images/image1.png b/src/doc/rustc/src/images/image1.png index ee2d3fd4f43c6..0da45e56620da 100644 Binary files a/src/doc/rustc/src/images/image1.png and b/src/doc/rustc/src/images/image1.png differ diff --git a/src/doc/rustc/src/images/image2.png b/src/doc/rustc/src/images/image2.png index 03061e1f0b12d..a9cf23f873772 100644 Binary files a/src/doc/rustc/src/images/image2.png and b/src/doc/rustc/src/images/image2.png differ diff --git a/src/doc/rustc/src/images/image3.png b/src/doc/rustc/src/images/image3.png index ef02c605ead8a..844a2fe67472d 100644 Binary files a/src/doc/rustc/src/images/image3.png and b/src/doc/rustc/src/images/image3.png differ