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| author | Oleg Nesterov <oleg@redhat.com> | 2009-09-05 11:17:13 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-09-05 11:30:42 -0700 |
| commit | a2a8474c3fff88d8dd52d05cb450563fb26fd26c (patch) | |
| tree | 455415da039a77627f47ed19318bb9c8aa17de4d /include | |
| parent | dd5d241ea955006122d76af88af87de73fec25b4 (diff) | |
| download | blackbird-op-linux-a2a8474c3fff88d8dd52d05cb450563fb26fd26c.tar.gz blackbird-op-linux-a2a8474c3fff88d8dd52d05cb450563fb26fd26c.zip | |
exec: do not sleep in TASK_TRACED under ->cred_guard_mutex
Tom Horsley reports that his debugger hangs when it tries to read
/proc/pid_of_tracee/maps, this happens since
"mm_for_maps: take ->cred_guard_mutex to fix the race with exec"
04b836cbf19e885f8366bccb2e4b0474346c02d
commit in 2.6.31.
But the root of the problem lies in the fact that do_execve() path calls
tracehook_report_exec() which can stop if the tracer sets PT_TRACE_EXEC.
The tracee must not sleep in TASK_TRACED holding this mutex. Even if we
remove ->cred_guard_mutex from mm_for_maps() and proc_pid_attr_write(),
another task doing PTRACE_ATTACH should not hang until it is killed or the
tracee resumes.
With this patch do_execve() does not use ->cred_guard_mutex directly and
we do not hold it throughout, instead:
- introduce prepare_bprm_creds() helper, it locks the mutex
and calls prepare_exec_creds() to initialize bprm->cred.
- install_exec_creds() drops the mutex after commit_creds(),
and thus before tracehook_report_exec()->ptrace_stop().
or, if exec fails,
free_bprm() drops this mutex when bprm->cred != NULL which
indicates install_exec_creds() was not called.
Reported-by: Tom Horsley <tom.horsley@att.net>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: David Howells <dhowells@redhat.com>
Cc: Roland McGrath <roland@redhat.com>
Cc: James Morris <jmorris@namei.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/binfmts.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h index 61ee18c1bdb4..2046b5b8af48 100644 --- a/include/linux/binfmts.h +++ b/include/linux/binfmts.h @@ -117,6 +117,7 @@ extern int setup_arg_pages(struct linux_binprm * bprm, int executable_stack); extern int bprm_mm_init(struct linux_binprm *bprm); extern int copy_strings_kernel(int argc,char ** argv,struct linux_binprm *bprm); +extern int prepare_bprm_creds(struct linux_binprm *bprm); extern void install_exec_creds(struct linux_binprm *bprm); extern void do_coredump(long signr, int exit_code, struct pt_regs *regs); extern int set_binfmt(struct linux_binfmt *new); |
