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GRUB module loading corruption #374

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marysaka opened this issue Jul 12, 2019 · 7 comments
Closed

GRUB module loading corruption #374

marysaka opened this issue Jul 12, 2019 · 7 comments
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@Orycterope
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help wanted Extra attention is needed project-kernel Related to the kernel type-bug Something isn't working

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@marysaka
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This memory corruption only occurs while loading vi and can be reproduced on PR #360 .
@marysaka marysaka added type-bug Something isn't working help wanted Extra attention is needed project-kernel Related to the kernel labels Jul 12, 2019
@roblabla
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d9c80bf is the commit that's affected (in case PR gets force pushed)

@Orycterope Orycterope mentioned this issue Jul 13, 2019
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@Orycterope
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Can you give a description of the problem ?

@marysaka marysaka mentioned this issue Jul 21, 2019
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@Orycterope Orycterope self-assigned this Jul 21, 2019
@Orycterope
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This bug is definitely present on master.

Haven't bisect yet, but reverting last xmas_elf update fixes the problem: 014dc18 (Jun 15 !)

I would like to investigate and report the bug to xmas_elf, but in the mean time I'm going to make a PR doing the revert.

Orycterope added a commit to Orycterope/SunriseOS that referenced this issue Jul 21, 2019
@Orycterope
Revert "Bump xmas-elf from 0.6.2 to 0.7.0"
9fec8a9 
This reverts commit 014dc18.

Addressing sunriseos#374

xmas_elf does an out of bound access when loading vi, causing a kernel panic.

Reverting the last update of xmas_elf seems to fix the problem, use this until we figure out where this bug comes from.
@Orycterope Orycterope mentioned this issue Jul 21, 2019
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@Orycterope Orycterope changed the title Memory corruption in Kernel ELF loader xmas_elf OOB access in Kernel ELF loader Jul 21, 2019
@Orycterope
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I was wrong, reverting xmas_elf update does no solve the problem. On some branches it seems to sometime disappear when doing a full rebuild of sunrise, hinting toward an incremental compilation problem.

For now I still believe this is a xmas_elf bug, and sunrise is not responsible for it. To prove my theory I'm going to try to replicate the OOB in a std crate that just tries to parse the "faulty" vi elf with xmas_elf.

@roblabla
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roblabla commented Jul 25, 2019 •
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@Thog found the problem: it's in mkiso-rs.

Once the bug is found, we should add a test to the CI that the generated ISO is correct by mounting the ISO and checking all the files.

EDIT: Such a test would not actually have found the problem, since the ISO filesystem seems to be OK. The El Torrito is apparently broken.

@marysaka
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GRUB2 seems to not like the way my files were allocated, this should be fixed by the last release of mkisofs-rs. Please make sure to update it.

@Orycterope
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Updated mkisofs-rs, diffed every module loaded by grub against their original elf, everything seems to be in order now.

I'm closing the issue.

@Orycterope Orycterope changed the title xmas_elf OOB access in Kernel ELF loader GRUB module loading corruption Jul 30, 2019
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@roblabla @marysaka @Orycterope