diff options
| author | Amulya Y <ayarlagadda@nvidia.com> | 2018-04-05 14:40:20 -0700 |
|---|---|---|
| committer | Winnie Hsu <whsu@nvidia.com> | 2018-04-19 10:57:54 -0700 |
| commit | c476b3908b73ae362945b9d14d620c0a09a8c539 (patch) | |
| tree | 8d320995bf1e81031369af6d82d471ccfdb93ab3 | |
| parent | 1de99ac66623dc420140c8a1a6c0271a553fe515 (diff) | |
proc:prevent /proc/PID/environ access until ready
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.
Bug 1823317
Bug 1935735
Change-Id: I38356eb68ffd1294f1f1250fb328bd01a3b37158
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>
Signed-off-by: Gagan Grover <ggrover@nvidia.com>
Signed-off-by: Amulya Yarlagadda <ayarlagadda@nvidia.com>
Reviewed-on: http://git-master/r/1259930
(cherry picked from commit 78d40f25b8e090782ca6b0c6051020557d373c92)
Reviewed-on: https://git-master.nvidia.com/r/1690302
Reviewed-by: Automatic_Commit_Validation_User
GVS: Gerrit_Virtual_Submit
Reviewed-by: Bibek Basu <bbasu@nvidia.com>
Reviewed-by: Winnie Hsu <whsu@nvidia.com>
| -rw-r--r-- | fs/proc/base.c | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/fs/proc/base.c b/fs/proc/base.c index 4823113f2584..464df13a1c19 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -46,7 +46,7 @@ * Paul Mundt <paul.mundt@nokia.com>: * Overall revision about smaps. * - * Copyright (c) 2013, NVIDIA CORPORATION. All rights reserved. + * Copyright (c) 2018, NVIDIA CORPORATION. All rights reserved. */ #include <asm/uaccess.h> @@ -857,7 +857,8 @@ static ssize_t environ_read(struct file *file, char __user *buf, int ret = 0; struct mm_struct *mm = file->private_data; - 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); |