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authorMathias Krause <minipli@googlemail.com>2016-05-05 16:22:26 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2016-05-11 11:21:16 +0200
commit898149d10b855a0d0a5a9f8f05e4359970919eb9 (patch)
tree589375a0686f79a185a7c87523803ba993ab83fa /fs
parent5fd407ad088227ee030e93246cffe757541483f0 (diff)
proc: prevent accessing /proc/<PID>/environ until it's ready
commit 8148a73c9901a8794a50f950083c00ccf97d43b3 upstream. 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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs')
-rw-r--r--fs/proc/base.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/fs/proc/base.c b/fs/proc/base.c
index b7de324bec11..e8bbf6cdb437 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -954,7 +954,8 @@ 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);