diff options
| author | Rich Felker <dalias@libc.org> | 2020-08-28 21:01:41 -0400 |
|---|---|---|
| committer | Rich Felker <dalias@libc.org> | 2020-09-13 21:22:55 -0400 |
| commit | b0cfc315ff38c423a5ce9ce159bd5baa4135e688 (patch) | |
| tree | d644d9e035223476718925fee68c57f1d13719a9 | |
| parent | ca6345de57a46ba1bd35bd15b0ceb42e05b3d71f (diff) | |
sh: fix syscall tracing
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.")
Tested-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Signed-off-by: Rich Felker <dalias@libc.org>
| -rw-r--r-- | arch/sh/kernel/entry-common.S | 1 | ||||
| -rw-r--r-- | arch/sh/kernel/ptrace_32.c | 15 |
2 files changed, 5 insertions, 11 deletions
diff --git a/arch/sh/kernel/entry-common.S b/arch/sh/kernel/entry-common.S index ad963104d22d..91ab2607a1ff 100644 --- a/arch/sh/kernel/entry-common.S +++ b/arch/sh/kernel/entry-common.S @@ -370,7 +370,6 @@ syscall_trace_entry: nop cmp/eq #-1, r0 bt syscall_exit - mov.l r0, @(OFF_R0,r15) ! Save return value ! Reload R0-R4 from kernel stack, where the ! parent may have modified them using ! ptrace(POKEUSR). (Note that R0-R2 are diff --git a/arch/sh/kernel/ptrace_32.c b/arch/sh/kernel/ptrace_32.c index b05bf92f9c32..5281685f6ad1 100644 --- a/arch/sh/kernel/ptrace_32.c +++ b/arch/sh/kernel/ptrace_32.c @@ -455,16 +455,11 @@ long arch_ptrace(struct task_struct *child, long request, asmlinkage long do_syscall_trace_enter(struct pt_regs *regs) { - long ret = 0; - if (test_thread_flag(TIF_SYSCALL_TRACE) && - tracehook_report_syscall_entry(regs)) - /* - * Tracing decided this syscall should not happen. - * We'll return a bogus call number to get an ENOSYS - * error, but leave the original number in regs->regs[0]. - */ - ret = -1L; + tracehook_report_syscall_entry(regs)) { + regs->regs[0] = -ENOSYS; + return -1; + } if (secure_computing() == -1) return -1; @@ -475,7 +470,7 @@ asmlinkage long do_syscall_trace_enter(struct pt_regs *regs) audit_syscall_entry(regs->regs[3], regs->regs[4], regs->regs[5], regs->regs[6], regs->regs[7]); - return ret ?: regs->regs[0]; + return 0; } asmlinkage void do_syscall_trace_leave(struct pt_regs *regs) |