diff options
| author | Mathias Krause <minipli@googlemail.com> | 2016-05-05 16:22:26 -0700 |
|---|---|---|
| committer | Alain Vongsouvanh <alainv@google.com> | 2016-11-03 15:25:57 +0000 |
| commit | d970acfebb8dc934874b552b46e8177552bc4838 (patch) | |
| tree | 26ccf93d19359cbedf98379d1cd2474ebb92b3e3 | |
| parent | 4790d258a37ff7ab012543b8c0cc38651bf2c7a1 (diff) | |
| download | bcm-d970acfebb8dc934874b552b46e8177552bc4838.tar.gz | |
proc: prevent accessing /proc/<PID>/environ until it's 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.
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>
(cherry picked from commit 8148a73c9901a8794a50f950083c00ccf97d43b3)
Change-Id: I59361ee8b6294499d9caa0f9556b4f9b7ba6954b
| -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 53aae7d7954..1434dbe7df1 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -850,7 +850,8 @@ 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); |