Patch "powerpc/perf: callchain validate kernel stack pointer bounds" has been added to the 5.15-stable tree

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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 5.15-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-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit c70f93766260616d8224c6b178e0d48a3d8706f9
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



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