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Rich Felker authored
Addition of SECCOMP_FILTER exposed a longstanding bug in do_syscall_trace_enter, whereby r0 (the 5th argument register) was mistakenly used where r3 (syscall_nr) was intended. By overwriting r0 rather than r3 with -1 when attempting to block a syscall, the existing code would instead have caused the syscall to execute with an argument clobbered. Commit 0bb605c2 then introduced skipping of the syscall when do_syscall_trace_enter returns -1, so that the return value set by seccomp filters would not be clobbered by -ENOSYS. This eliminated the clobbering of the 5th argument register, but instead caused syscalls made with a 5th argument of -1 to be misinterpreted as a request by do_syscall_trace_enter to suppress the syscall. Fixes: 0bb605c2 ("sh: Add SECCOMP_FILTER") Fixes: ab99c733 ("sh: Make syscall tracer use tracehook notifiers, add TIF_NOTIFY_RESUME.") Tested-by:
John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de> Signed-off-by:
Rich Felker <dalias@libc.org>
b0cfc315