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author | Stephen Wilson <wilsons@start.ca> | 2011-03-13 15:49:22 -0400 |
---|---|---|
committer | Al Viro <viro@zeniv.linux.org.uk> | 2011-03-23 16:36:58 -0400 |
commit | 18f661bcf898742212182d75f22f05b048cc04bb (patch) | |
tree | 3a0a6edc6e4240bda06fe52d565fe4b1cb4d8b84 | |
parent | 26947f8c8f9598209001cdcd31bb2162a2e54691 (diff) | |
download | op-kernel-dev-18f661bcf898742212182d75f22f05b048cc04bb.zip op-kernel-dev-18f661bcf898742212182d75f22f05b048cc04bb.tar.gz |
proc: hold cred_guard_mutex in check_mem_permission()
Avoid a potential race when task exec's and we get a new ->mm but check against
the old credentials in ptrace_may_access().
Holding of the mutex is implemented by factoring out the body of the code into a
helper function __check_mem_permission(). Performing this factorization now
simplifies upcoming changes and minimizes churn in the diff's.
Signed-off-by: Stephen Wilson <wilsons@start.ca>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
-rw-r--r-- | fs/proc/base.c | 26 |
1 files changed, 22 insertions, 4 deletions
diff --git a/fs/proc/base.c b/fs/proc/base.c index 9af49a3..013f116 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -191,10 +191,7 @@ static int proc_root_link(struct inode *inode, struct path *path) return result; } -/* - * Return zero if current may access user memory in @task, -error if not. - */ -static int check_mem_permission(struct task_struct *task) +static int __check_mem_permission(struct task_struct *task) { /* * A task can always look at itself, in case it chooses @@ -222,6 +219,27 @@ static int check_mem_permission(struct task_struct *task) return -EPERM; } +/* + * Return zero if current may access user memory in @task, -error if not. + */ +static int check_mem_permission(struct task_struct *task) +{ + int err; + + /* + * Avoid racing if task exec's as we might get a new mm but validate + * against old credentials. + */ + err = mutex_lock_killable(&task->signal->cred_guard_mutex); + if (err) + return err; + + err = __check_mem_permission(task); + mutex_unlock(&task->signal->cred_guard_mutex); + + return err; +} + struct mm_struct *mm_for_maps(struct task_struct *task) { struct mm_struct *mm; |