[PATCH] Fix unserialized task->files changing
Fixed race on put_files_struct on exec with proc. Restoring files on
current on error path may lead to proc having a pointer to already kfree-d
files_struct.
->files changing at exit.c and khtread.c are safe as exit_files() makes all
things under lock.
Found during OpenVZ stress testing.
[akpm@osdl.org: add export]
Signed-off-by: Pavel Emelianov <xemul@openvz.org>
Signed-off-by: Kirill Korotaev <dev@openvz.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index dfd8cfb..bb43da5 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1038,10 +1038,8 @@
out_free_file:
sys_close(elf_exec_fileno);
out_free_fh:
- if (files) {
- put_files_struct(current->files);
- current->files = files;
- }
+ if (files)
+ reset_files_struct(current, files);
out_free_ph:
kfree(elf_phdata);
goto out;
diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c
index 66ba137..1713c48 100644
--- a/fs/binfmt_misc.c
+++ b/fs/binfmt_misc.c
@@ -215,10 +215,8 @@
bprm->interp_flags = 0;
bprm->interp_data = 0;
_unshare:
- if (files) {
- put_files_struct(current->files);
- current->files = files;
- }
+ if (files)
+ reset_files_struct(current, files);
goto _ret;
}
diff --git a/fs/exec.c b/fs/exec.c
index 97df6e0..a8efe35 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -898,8 +898,7 @@
return 0;
mmap_failed:
- put_files_struct(current->files);
- current->files = files;
+ reset_files_struct(current, files);
out:
return retval;
}
diff --git a/include/linux/file.h b/include/linux/file.h
index 9f7c251..74183e6 100644
--- a/include/linux/file.h
+++ b/include/linux/file.h
@@ -112,5 +112,6 @@
struct files_struct *get_files_struct(struct task_struct *);
void FASTCALL(put_files_struct(struct files_struct *fs));
+void reset_files_struct(struct task_struct *, struct files_struct *);
#endif /* __LINUX_FILE_H */
diff --git a/kernel/exit.c b/kernel/exit.c
index d891883..4b6fb05 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -487,6 +487,18 @@
EXPORT_SYMBOL(put_files_struct);
+void reset_files_struct(struct task_struct *tsk, struct files_struct *files)
+{
+ struct files_struct *old;
+
+ old = tsk->files;
+ task_lock(tsk);
+ tsk->files = files;
+ task_unlock(tsk);
+ put_files_struct(old);
+}
+EXPORT_SYMBOL(reset_files_struct);
+
static inline void __exit_files(struct task_struct *tsk)
{
struct files_struct * files = tsk->files;