From: Kees Cook Date: Sat, 12 Sep 2020 00:58:26 +0000 (-0700) Subject: core/entry: Report syscall correctly for trace and audit X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=b6ec41346103;p=linux.git core/entry: Report syscall correctly for trace and audit On v5.8 when doing seccomp syscall rewrites (e.g. getpid into getppid as seen in the seccomp selftests), trace (and audit) correctly see the rewritten syscall on entry and exit: seccomp_bpf-1307 [000] .... 22974.874393: sys_enter: NR 110 (... seccomp_bpf-1307 [000] .N.. 22974.874401: sys_exit: NR 110 = 1304 With mainline we see a mismatched enter and exit (the original syscall is incorrectly visible on entry): seccomp_bpf-1030 [000] .... 21.806766: sys_enter: NR 39 (... seccomp_bpf-1030 [000] .... 21.806767: sys_exit: NR 110 = 1027 When ptrace or seccomp change the syscall, this needs to be visible to trace and audit at that time as well. Update the syscall earlier so they see the correct value. Fixes: d88d59b64ca3 ("core/entry: Respect syscall number rewrites") Reported-by: Michael Ellerman Signed-off-by: Kees Cook Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20200912005826.586171-1-keescook@chromium.org --- diff --git a/kernel/entry/common.c b/kernel/entry/common.c index 18683598edbc6..6fdb6105e6d61 100644 --- a/kernel/entry/common.c +++ b/kernel/entry/common.c @@ -60,13 +60,15 @@ static long syscall_trace_enter(struct pt_regs *regs, long syscall, return ret; } + /* Either of the above might have changed the syscall number */ + syscall = syscall_get_nr(current, regs); + if (unlikely(ti_work & _TIF_SYSCALL_TRACEPOINT)) trace_sys_enter(regs, syscall); syscall_enter_audit(regs, syscall); - /* The above might have changed the syscall number */ - return ret ? : syscall_get_nr(current, regs); + return ret ? : syscall; } static __always_inline long