[PATCH 10/12] proc: hold cred_guard_mutex in check_mem_permission()
From: Stephen Wilson <hidden>
Date: 2011-03-13 19:56:56
Also in:
lkml
Subsystem:
filesystems (vfs and infrastructure), proc filesystem, the rest · Maintainers:
Alexander Viro, Christian Brauner, Linus Torvalds
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 <redacted> --- 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 e52702d..f6b644f 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;
--
1.7.3.5
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