From 3b9b8ab65d8eed784b9164d03807cb2bda7b5cd6 Mon Sep 17 00:00:00 2001 From: Kirill Korotaev Date: Fri, 29 Sep 2006 02:00:05 -0700 Subject: [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 Signed-off-by: Kirill Korotaev Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/binfmt_elf.c | 6 ++---- fs/binfmt_misc.c | 6 ++---- fs/exec.c | 3 +-- include/linux/file.h | 1 + kernel/exit.c | 12 ++++++++++++ 5 files changed, 18 insertions(+), 10 deletions(-) diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index dfd8cfb7fb5..bb43da5cde5 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -1038,10 +1038,8 @@ out_free_interp: 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 66ba137f866..1713c48fef5 100644 --- a/fs/binfmt_misc.c +++ b/fs/binfmt_misc.c @@ -215,10 +215,8 @@ _error: 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 97df6e0aeae..a8efe35176b 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -898,8 +898,7 @@ int flush_old_exec(struct linux_binprm * bprm) 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 9f7c2513866..74183e6f7f4 100644 --- a/include/linux/file.h +++ b/include/linux/file.h @@ -112,5 +112,6 @@ struct task_struct; 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 d891883420f..4b6fb054b25 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -487,6 +487,18 @@ void fastcall put_files_struct(struct files_struct *files) 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; -- cgit v1.2.3