From: Mathias Krause <minipli@googlemail.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org,
Mathias Krause <minipli@googlemail.com>,
Emese Revfy <re.emese@gmail.com>, Pax Team <pageexec@freemail.hu>,
Al Viro <viro@zeniv.linux.org.uk>,
Mateusz Guzik <mguzik@redhat.com>,
Alexey Dobriyan <adobriyan@gmail.com>,
Cyrill Gorcunov <gorcunov@openvz.org>,
Jarod Wilson <jarod@redhat.com>
Subject: [PATCH] proc: prevent accessing /proc/<PID>/environ until it's ready
Date: Thu, 28 Apr 2016 21:04:18 +0200 [thread overview]
Message-ID: <1461870258-17970-1-git-send-email-minipli@googlemail.com> (raw)
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.
Reported-at: https://forums.grsecurity.net/viewtopic.php?f=3&t=4363
Bugzilla: 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>
---
fs/proc/base.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 4f764c2ac1a5..45f2162e55b2 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -955,7 +955,8 @@ static ssize_t environ_read(struct file *file, char __user *buf,
struct mm_struct *mm = file->private_data;
unsigned long env_start, env_end;
- 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);
--
1.7.10.4
next reply other threads:[~2016-04-28 19:04 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-28 19:04 Mathias Krause [this message]
2016-04-28 19:20 ` [PATCH] proc: prevent accessing /proc/<PID>/environ until it's ready Mateusz Guzik
2016-04-28 19:36 ` Mathias Krause
2016-04-29 10:11 ` Alexey Dobriyan
2016-04-28 19:28 ` Cyrill Gorcunov
2016-04-28 21:26 ` Andrew Morton
2016-04-29 5:59 ` Mathias Krause
2016-04-28 21:30 ` Andrew Morton
2016-04-29 6:02 ` Mathias Krause
2016-04-29 10:25 ` Alexey Dobriyan
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