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powerpc/perf: callchain validate kernel stack pointer bounds

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[ Upstream commit 32c5209214bd8d4f8c4e9d9b630ef4c671f58e79 ]

The interrupt frame detection and loads from the hypothetical pt_regs
are not bounds-checked. The next-frame validation only bounds-checks
STACK_FRAME_OVERHEAD, which does not include the pt_regs. Add another
test for this.

The user could set r1 to be equal to the address matching the first
interrupt frame - STACK_INT_FRAME_SIZE, which is in the previous page
due to the kernel redzone, and induce the kernel to load the marker from
there. Possibly this could cause a crash at least. If the user could
induce the previous page to contain a valid marker, then it might be
able to direct perf to read specific memory addresses in a way that
could be transmitted back to the user in the perf data.

Fixes: 20002ded4d ("perf_counter: powerpc: Add callchain support")
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20221127124942.1665522-4-npiggin@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Nicholas Piggin 2022-11-27 22:49:28 +10:00 committed by Greg Kroah-Hartman
parent cfb5bbfcb6
commit d539b77bae
1 changed files with 1 additions and 0 deletions
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arch/powerpc/perf/callchain.c
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@ -64,6 +64,7 @@ perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, struct pt_regs *re
next_sp = fp[0];
if (next_sp == sp + STACK_INT_FRAME_SIZE &&
validate_sp(sp, current, STACK_INT_FRAME_SIZE) &&
fp[STACK_FRAME_MARKER] == STACK_FRAME_REGS_MARKER) {
/*
* This looks like an interrupt frame for an