diff options
| author | Jann Horn <jannh@google.com> | 2018-06-25 18:34:19 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-09-09 20:01:24 +0200 |
| commit | a56a15432ac808d63d7c3b24fa81dfa6afbab067 (patch) | |
| tree | d1f34082f822c66722da0e0e831bcf8c5df93699 | |
| parent | 55463c60b7d56e98936abfd092b4983dd010df50 (diff) | |
userns: move user access out of the mutex
commit 5820f140edef111a9ea2ef414ab2428b8cb805b1 upstream.
The old code would hold the userns_state_mutex indefinitely if
memdup_user_nul stalled due to e.g. a userfault region. Prevent that by
moving the memdup_user_nul in front of the mutex_lock().
Note: This changes the error precedence of invalid buf/count/*ppos vs
map already written / capabilities missing.
Fixes: 22d917d80e84 ("userns: Rework the user_namespace adding uid/gid...")
Cc: stable@vger.kernel.org
Signed-off-by: Jann Horn <jannh@google.com>
Acked-by: Christian Brauner <christian@brauner.io>
Acked-by: Serge Hallyn <serge@hallyn.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | kernel/user_namespace.c | 24 |
1 files changed, 10 insertions, 14 deletions
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c index 86b7854fec8e..f789bbba9b8e 100644 --- a/kernel/user_namespace.c +++ b/kernel/user_namespace.c @@ -649,7 +649,16 @@ static ssize_t map_write(struct file *file, const char __user *buf, unsigned idx; struct uid_gid_extent *extent = NULL; char *kbuf = NULL, *pos, *next_line; - ssize_t ret = -EINVAL; + ssize_t ret; + + /* Only allow < page size writes at the beginning of the file */ + if ((*ppos != 0) || (count >= PAGE_SIZE)) + return -EINVAL; + + /* Slurp in the user data */ + kbuf = memdup_user_nul(buf, count); + if (IS_ERR(kbuf)) + return PTR_ERR(kbuf); /* * The userns_state_mutex serializes all writes to any given map. @@ -683,19 +692,6 @@ static ssize_t map_write(struct file *file, const char __user *buf, if (cap_valid(cap_setid) && !file_ns_capable(file, ns, CAP_SYS_ADMIN)) goto out; - /* Only allow < page size writes at the beginning of the file */ - ret = -EINVAL; - if ((*ppos != 0) || (count >= PAGE_SIZE)) - goto out; - - /* Slurp in the user data */ - kbuf = memdup_user_nul(buf, count); - if (IS_ERR(kbuf)) { - ret = PTR_ERR(kbuf); - kbuf = NULL; - goto out; - } - /* Parse the user data */ ret = -EINVAL; pos = kbuf; |