From: Nicholas Piggin npiggin@gmail.com
[ 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@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 --- arch/powerpc/perf/callchain.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/arch/powerpc/perf/callchain.c b/arch/powerpc/perf/callchain.c index 0fc26714780a..a4c4685096f8 100644 --- a/arch/powerpc/perf/callchain.c +++ b/arch/powerpc/perf/callchain.c @@ -67,6 +67,7 @@ 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