Messages in this thread Patch in this message | | | Date | Mon, 9 Feb 2009 02:02:33 +0100 | From | Oleg Nesterov <> | Subject | [PATCH, for 2.6.29] ptrace: fix the usage of ptrace_fork() |
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I noticed by pure accident we have ptrace_fork() and friends. This was added by "x86, bts: add fork and exit handling", commit bf53de907dfdaac178c92d774aae7370d7b97d20
I can't test this, ds_request_bts() returns -EOPNOTSUPP, but I strongly believe this needs the fix. I think something like this program
int main(void) { int pid = fork();
if (!pid) { ptrace(PTRACE_TRACEME, 0, NULL, NULL); kill(getpid(), SIGSTOP); fork(); } else { struct ptrace_bts_config bts = { .flags = PTRACE_BTS_O_ALLOC, .size = 4 * 4096, };
wait(NULL);
ptrace(PTRACE_SETOPTIONS, pid, NULL, PTRACE_O_TRACEFORK); ptrace(PTRACE_BTS_CONFIG, pid, &bts, sizeof(bts)); ptrace(PTRACE_CONT, pid, NULL, NULL);
sleep(1); }
return 0; }
should crash the kernel.
If the task is traced by its natural parent ptrace_reparented() returns 0 but we should clear ->btsxxx anyway.
This is a minimal fix for 2.6.29, we need further cleanups imho.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
--- 6.29-rc3/kernel/fork.c~BTS_FIX 2009-01-29 01:13:55.000000000 +0100 +++ 6.29-rc3/kernel/fork.c 2009-02-09 01:03:48.000000000 +0100 @@ -1093,7 +1093,7 @@ static struct task_struct *copy_process( #ifdef CONFIG_DEBUG_MUTEXES p->blocked_on = NULL; /* not blocked yet */ #endif - if (unlikely(ptrace_reparented(current))) + if (unlikely(current->ptrace)) ptrace_fork(p, clone_flags); /* Perform scheduler related setup. Assign this task to a CPU. */
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