diff options
| author | Mathias Krause <minipli@googlemail.com> | 2016-05-05 16:22:26 -0700 |
|---|---|---|
| committer | Mister Oyster <oysterized@gmail.com> | 2017-04-11 10:57:33 +0200 |
| commit | 739d6b2fe12e7e0775677b651a9b66c82b20411e (patch) | |
| tree | e5a8cc9f53925b0f625aad865e478cfe9e035e0c /fs/proc | |
| parent | e9e6855ea82e3fe6c5e447ef397fd3aa5aaffbd7 (diff) | |
UPSTREAM: proc: prevent accessing /proc/<PID>/environ until it's ready
(cherry picked from commit 8148a73c9901a8794a50f950083c00ccf97d43b3)
If /proc/<PID>/environ gets read before the envp[] array is fully set up
in create_{aout,elf,elf_fdpic,flat}_tables(), we might end up trying to
read more bytes than are actually written, as env_start will already be
set but env_end will still be zero, making the range calculation
underflow, allowing to read beyond the end of what has been written.
Fix this as it is done for /proc/<PID>/cmdline by testing env_end for
zero. It is, apparently, intentionally set last in create_*_tables().
This bug was found by the PaX size_overflow plugin that detected the
arithmetic underflow of 'this_len = env_end - (env_start + src)' when
env_end is still zero.
The expected consequence is that userland trying to access
/proc/<PID>/environ of a not yet fully set up process may get
inconsistent data as we're in the middle of copying in the environment
variables.
Fixes: https://forums.grsecurity.net/viewtopic.php?f=3&t=4363
Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=116461
Signed-off-by: Mathias Krause <minipli@googlemail.com>
Cc: Emese Revfy <re.emese@gmail.com>
Cc: Pax Team <pageexec@freemail.hu>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Mateusz Guzik <mguzik@redhat.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Jarod Wilson <jarod@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Change-Id: Ia2f58d48c15478ed4b6e237b63e704c70ff21e96
Bug: 30951939
Diffstat (limited to 'fs/proc')
| -rw-r--r-- | fs/proc/base.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/fs/proc/base.c b/fs/proc/base.c index 1d1561a6c..d909b2f18 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -755,7 +755,8 @@ static ssize_t mem_rw(struct file *file, char __user *buf, ssize_t copied; char *page; - if (!mm) + /* Ensure the process spawned far enough to have an environment. */ + if (!mm || !mm->env_end) return 0; page = (char *)__get_free_page(GFP_TEMPORARY); |