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| author | Roland McGrath <roland@redhat.com> | 2007-09-05 03:05:56 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-09-10 18:57:47 -0700 |
| commit | 7d94143291e4e625e2bc3b1ebdc7143ee7a9a2f1 (patch) | |
| tree | c4f8a974a33dd6ac1feacf18f217ee326c8af5eb /kernel | |
| parent | 897ee77bfba12b83752027427a41009961458ee6 (diff) | |
| download | lwn-7d94143291e4e625e2bc3b1ebdc7143ee7a9a2f1.tar.gz lwn-7d94143291e4e625e2bc3b1ebdc7143ee7a9a2f1.zip | |
Fix spurious syscall tracing after PTRACE_DETACH + PTRACE_ATTACH
When PTRACE_SYSCALL was used and then PTRACE_DETACH is used, the
TIF_SYSCALL_TRACE flag is left set on the formerly-traced task. This
means that when a new tracer comes along and does PTRACE_ATTACH, it's
possible he gets a syscall tracing stop even though he's never used
PTRACE_SYSCALL. This happens if the task was in the middle of a system
call when the second PTRACE_ATTACH was done. The symptom is an
unexpected SIGTRAP when the tracer thinks that only SIGSTOP should have
been provoked by his ptrace calls so far.
A few machines already fixed this in ptrace_disable (i386, ia64, m68k).
But all other machines do not, and still have this bug. On x86_64, this
constitutes a regression in IA32 compatibility support.
Since all machines now use TIF_SYSCALL_TRACE for this, I put the
clearing of TIF_SYSCALL_TRACE in the generic ptrace_detach code rather
than adding it to every other machine's ptrace_disable.
Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/ptrace.c | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/kernel/ptrace.c b/kernel/ptrace.c index 82a558b655da..3eca7a55f2ee 100644 --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -233,6 +233,7 @@ int ptrace_detach(struct task_struct *child, unsigned int data) /* Architecture-specific hardware disable .. */ ptrace_disable(child); + clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE); write_lock_irq(&tasklist_lock); /* protect against de_thread()->release_task() */ |