Messages in this thread | | | Subject | Re: [PATCH] sh: fix syscall tracing | From | John Paul Adrian Glaubitz <> | Date | Thu, 3 Sep 2020 10:13:43 +0200 |
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Hi Rich!
On 9/3/20 7:48 AM, Rich Felker wrote: > 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 0bb605c2c7f2b4b3 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: 0bb605c2c7f2b4b3 ("sh: Add SECCOMP_FILTER") > Fixes: ab99c733ae73cce3 ("sh: Make syscall tracer use tracehook notifiers, add TIF_NOTIFY_RESUME.") > Signed-off-by: Rich Felker <dalias@libc.org>
I'm testing this patch now with a rebased kernel and a rebased libseccomp with my patch for SuperH support on top.
I'll report back later.
Adrian
-- .''`. John Paul Adrian Glaubitz : :' : Debian Developer - glaubitz@debian.org `. `' Freie Universitaet Berlin - glaubitz@physik.fu-berlin.de `- GPG: 62FF 8A75 84E0 2956 9546 0006 7426 3B37 F5B5 F913
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