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arm64: fix possible spectre-v1 write in ptrace_hbp_set_event()

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It's possible for userspace to control idx. Sanitize idx when using it
as an array index, to inhibit the potential spectre-v1 write gadget.

Found by smatch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Mark Rutland 2018-07-10 19:01:22 +01:00 committed by Will Deacon
parent 11527b3e0b
commit 14d6e289a8
1 changed files with 11 additions and 8 deletions
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19
arch/arm64/kernel/ptrace.c
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@ -277,19 +277,22 @@ static int ptrace_hbp_set_event(unsigned int note_type,
switch (note_type) {
case NT_ARM_HW_BREAK:
if (idx < ARM_MAX_BRP) {
tsk->thread.debug.hbp_break[idx] = bp;
err = 0;
}
if (idx >= ARM_MAX_BRP)
goto out;
idx = array_index_nospec(idx, ARM_MAX_BRP);
tsk->thread.debug.hbp_break[idx] = bp;
err = 0;
break;
case NT_ARM_HW_WATCH:
if (idx < ARM_MAX_WRP) {
tsk->thread.debug.hbp_watch[idx] = bp;
err = 0;
}
if (idx >= ARM_MAX_WRP)
goto out;
idx = array_index_nospec(idx, ARM_MAX_WRP);
tsk->thread.debug.hbp_watch[idx] = bp;
err = 0;
break;
}
out:
return err;
}