This is a note to let you know that I've just added the patch titled powerpc/perf: callchain validate kernel stack pointer bounds to the 6.1-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: powerpc-perf-callchain-validate-kernel-stack-pointer.patch and it can be found in the queue-6.1 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 1517c6a21a60586ada1d606040f54e13a13fc37a Author: Nicholas Piggin <npiggin@xxxxxxxxx> Date: Sun Nov 27 22:49:28 2022 +1000 powerpc/perf: callchain validate kernel stack pointer bounds [ 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: 20002ded4d93 ("perf_counter: powerpc: Add callchain support") Signed-off-by: Nicholas Piggin <npiggin@xxxxxxxxx> Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20221127124942.1665522-4-npiggin@xxxxxxxxx Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/arch/powerpc/perf/callchain.c b/arch/powerpc/perf/callchain.c index 082f6d0308a4..8718289c051d 100644 --- a/arch/powerpc/perf/callchain.c +++ b/arch/powerpc/perf/callchain.c @@ -61,6 +61,7 @@ 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