Re: [PATCH] powerpc/64/syscall: Disable sanitisers for C syscall entry/exit code
From: Andrew Donnellan <hidden>
Date: 2020-05-29 08:26:53
On 29/5/20 4:14 pm, Daniel Axtens wrote:
quoted hunk ↗ jump to hunk
syzkaller is picking up a bunch of crashes that look like this: Unrecoverable exception 380 at c00000000037ed60 (msr=8000000000001031) Oops: Unrecoverable exception, sig: 6 [#1] LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries Modules linked in: CPU: 0 PID: 874 Comm: syz-executor.0 Not tainted 5.7.0-rc7-syzkaller-00016-gb0c3ba31be3e #0 NIP: c00000000037ed60 LR: c00000000004bac8 CTR: c000000000030990 REGS: c0000000555a7230 TRAP: 0380 Not tainted (5.7.0-rc7-syzkaller-00016-gb0c3ba31be3e) MSR: 8000000000001031 <SF,ME,IR,DR,LE> CR: 48222882 XER: 20000000 CFAR: c00000000004bac4 IRQMASK: 0 GPR00: c00000000004bb68 c0000000555a74c0 c0000000024b3500 0000000000000005 GPR04: 0000000000000000 0000000000000000 c00000000004bb88 c008000000910000 GPR08: 00000000000b0000 c00000000004bac8 0000000000016000 c000000002503500 GPR12: c000000000030990 c000000003190000 00000000106a5898 00000000106a0000 GPR16: 00000000106a5890 c000000007a92000 c000000008180e00 c000000007a8f700 GPR20: c000000007a904b0 0000000010110000 c00000000259d318 5deadbeef0000100 GPR24: 5deadbeef0000122 c000000078422700 c000000009ee88b8 c000000078422778 GPR28: 0000000000000001 800000000280b033 0000000000000000 c0000000555a75a0 NIP [c00000000037ed60] __sanitizer_cov_trace_pc+0x40/0x50 LR [c00000000004bac8] interrupt_exit_kernel_prepare+0x118/0x310 Call Trace: [c0000000555a74c0] [c00000000004bb68] interrupt_exit_kernel_prepare+0x1b8/0x310 (unreliable) [c0000000555a7530] [c00000000000f9a8] interrupt_return+0x118/0x1c0--- interrupt: 900 at __sanitizer_cov_trace_pc+0x0/0x50...<random previous call chain>... That looks like the KCOV helper accessing memory that's not safe to access in the interrupt handling context. Do not instrument the new syscall entry/exit code with KCOV, GCOV or UBSAN. Cc: Nicholas Piggin <npiggin@gmail.com> Fixes: 68b34588e202 ("powerpc/64/sycall: Implement syscall entry/exit logic in C") Signed-off-by: Daniel Axtens <redacted>
This seems reasonable - I've verified that this does indeed suppress the kcov trace calls. Acked-by: Andrew Donnellan <redacted> (does this need to be tagged for stable? the Fixes: commit is in 5.6 but we're at 5.7-rc7 at this point...) -- Andrew Donnellan OzLabs, ADL Canberra ajd@linux.ibm.com IBM Australia Limited