Differential D34594

arm: Zero padding in mcontext_vfp_t in get_vfpcontext().
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Authored by jhb on Mar 17 2022, 10:34 PM.

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markj
andrew
imp

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rGfb3fa01a2df5: arm: Zero padding in mcontext_vfp_t in get_vfpcontext().
rGb234b8d911cd: arm: Zero padding in mcontext_vfp_t in get_vfpcontext().

Summary

This can leak kernel stack data otherwise.

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rS FreeBSD src repository - subversion

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Buildable 44816
Build 41704: arc lint + arc unit

Event Timeline

jhb created this revision.Mar 17 2022, 10:34 PM

Herald added a subscriber: imp. · View Herald TranscriptMar 17 2022, 10:34 PM

jhb requested review of this revision.Mar 17 2022, 10:34 PM

Harbormaster completed remote builds in B44816: Diff 103966.Mar 17 2022, 10:34 PM

markj accepted this revision.Mar 17 2022, 10:38 PM

This revision is now accepted and ready to land.Mar 17 2022, 10:38 PM

So it's fine as is, but a pad might be better...

sys/arm/arm/exec_machdep.c
113	Or we could add a a 'mcv_pad' int32_t field and just set that... It's the only bytes that need to be set and setting the other 32*8+4 (260 bytes)....

andrew added inline comments.Mar 18 2022, 11:14 AM

sys/arm/arm/exec_machdep.c
113	We should put a pad field in as the compiler could still leak kernel stack data via the padding.

jhb added inline comments.Mar 23 2022, 8:25 PM

sys/arm/arm/exec_machdep.c
113	Modern compilers are smart enough given that memcpy and memset are builtins to only memset the bits that aren't overwritten by the memcpy. I'm not sure of the value of making the padding field explicit?

Closed by commit rGb234b8d911cd: arm: Zero padding in mcontext_vfp_t in get_vfpcontext(). (authored by jhb). · Explain WhyMar 25 2022, 5:00 PM

This revision was automatically updated to reflect the committed changes.

jhb added a commit: rGb234b8d911cd: arm: Zero padding in mcontext_vfp_t in get_vfpcontext()..

jhb added a commit: rGfb3fa01a2df5: arm: Zero padding in mcontext_vfp_t in get_vfpcontext()..May 13 2022, 5:43 PM

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sys/

arm/

arm/

1 line

Diff 103966

sys/arm/arm/exec_machdep.c

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