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authorAmulya Y <ayarlagadda@nvidia.com>2018-04-05 14:40:20 -0700
committerWinnie Hsu <whsu@nvidia.com>2018-04-19 10:57:54 -0700
commitc476b3908b73ae362945b9d14d620c0a09a8c539 (patch)
tree8d320995bf1e81031369af6d82d471ccfdb93ab3 /fs
parent1de99ac66623dc420140c8a1a6c0271a553fe515 (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>
Diffstat (limited to 'fs')
-rw-r--r--fs/proc/base.c5
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);