[3.13.y.z extended stable] Patch "net: sendmsg: fix NULL pointer dereference" has been added to staging queue
Kamal Mostafa
kamal at canonical.com
Thu Aug 7 21:55:42 UTC 2014
This is a note to let you know that I have just added a patch titled
net: sendmsg: fix NULL pointer dereference
to the linux-3.13.y-queue branch of the 3.13.y.z extended stable tree
which can be found at:
http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue
This patch is scheduled to be released in version 3.13.11.6.
If you, or anyone else, feels it should not be added to this tree, please
reply to this email.
For more information about the 3.13.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable
Thanks.
-Kamal
------
>From 158c3d64222d3d9eac8eb88350224b391f6b959d Mon Sep 17 00:00:00 2001
From: Andrey Ryabinin <ryabinin.a.a at gmail.com>
Date: Sat, 26 Jul 2014 21:26:58 +0400
Subject: net: sendmsg: fix NULL pointer dereference
commit 40eea803c6b2cfaab092f053248cbeab3f368412 upstream.
Sasha's report:
> While fuzzing with trinity inside a KVM tools guest running the latest -next
> kernel with the KASAN patchset, I've stumbled on the following spew:
>
> [ 4448.949424] ==================================================================
> [ 4448.951737] AddressSanitizer: user-memory-access on address 0
> [ 4448.952988] Read of size 2 by thread T19638:
> [ 4448.954510] CPU: 28 PID: 19638 Comm: trinity-c76 Not tainted 3.16.0-rc4-next-20140711-sasha-00046-g07d3099-dirty #813
> [ 4448.956823] ffff88046d86ca40 0000000000000000 ffff880082f37e78 ffff880082f37a40
> [ 4448.958233] ffffffffb6e47068 ffff880082f37a68 ffff880082f37a58 ffffffffb242708d
> [ 4448.959552] 0000000000000000 ffff880082f37a88 ffffffffb24255b1 0000000000000000
> [ 4448.961266] Call Trace:
> [ 4448.963158] dump_stack (lib/dump_stack.c:52)
> [ 4448.964244] kasan_report_user_access (mm/kasan/report.c:184)
> [ 4448.965507] __asan_load2 (mm/kasan/kasan.c:352)
> [ 4448.966482] ? netlink_sendmsg (net/netlink/af_netlink.c:2339)
> [ 4448.967541] netlink_sendmsg (net/netlink/af_netlink.c:2339)
> [ 4448.968537] ? get_parent_ip (kernel/sched/core.c:2555)
> [ 4448.970103] sock_sendmsg (net/socket.c:654)
> [ 4448.971584] ? might_fault (mm/memory.c:3741)
> [ 4448.972526] ? might_fault (./arch/x86/include/asm/current.h:14 mm/memory.c:3740)
> [ 4448.973596] ? verify_iovec (net/core/iovec.c:64)
> [ 4448.974522] ___sys_sendmsg (net/socket.c:2096)
> [ 4448.975797] ? put_lock_stats.isra.13 (./arch/x86/include/asm/preempt.h:98 kernel/locking/lockdep.c:254)
> [ 4448.977030] ? lock_release_holdtime (kernel/locking/lockdep.c:273)
> [ 4448.978197] ? lock_release_non_nested (kernel/locking/lockdep.c:3434 (discriminator 1))
> [ 4448.979346] ? check_chain_key (kernel/locking/lockdep.c:2188)
> [ 4448.980535] __sys_sendmmsg (net/socket.c:2181)
> [ 4448.981592] ? trace_hardirqs_on_caller (kernel/locking/lockdep.c:2600)
> [ 4448.982773] ? trace_hardirqs_on (kernel/locking/lockdep.c:2607)
> [ 4448.984458] ? syscall_trace_enter (arch/x86/kernel/ptrace.c:1500 (discriminator 2))
> [ 4448.985621] ? trace_hardirqs_on_caller (kernel/locking/lockdep.c:2600)
> [ 4448.986754] SyS_sendmmsg (net/socket.c:2201)
> [ 4448.987708] tracesys (arch/x86/kernel/entry_64.S:542)
> [ 4448.988929] ==================================================================
This reports means that we've come to netlink_sendmsg() with msg->msg_name == NULL and msg->msg_namelen > 0.
After this report there was no usual "Unable to handle kernel NULL pointer dereference"
and this gave me a clue that address 0 is mapped and contains valid socket address structure in it.
This bug was introduced in f3d3342602f8bcbf37d7c46641cb9bca7618eb1c
(net: rework recvmsg handler msg_name and msg_namelen logic).
Commit message states that:
"Set msg->msg_name = NULL if user specified a NULL in msg_name but had a
non-null msg_namelen in verify_iovec/verify_compat_iovec. This doesn't
affect sendto as it would bail out earlier while trying to copy-in the
address."
But in fact this affects sendto when address 0 is mapped and contains
socket address structure in it. In such case copy-in address will succeed,
verify_iovec() function will successfully exit with msg->msg_namelen > 0
and msg->msg_name == NULL.
This patch fixes it by setting msg_namelen to 0 if msg_name == NULL.
Cc: Hannes Frederic Sowa <hannes at stressinduktion.org>
Cc: Eric Dumazet <edumazet at google.com>
Reported-by: Sasha Levin <sasha.levin at oracle.com>
Signed-off-by: Andrey Ryabinin <a.ryabinin at samsung.com>
Acked-by: Hannes Frederic Sowa <hannes at stressinduktion.org>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
net/compat.c | 9 +++++----
net/core/iovec.c | 6 +++---
2 files changed, 8 insertions(+), 7 deletions(-)
diff --git a/net/compat.c b/net/compat.c
index f50161f..cbc1a2a 100644
--- a/net/compat.c
+++ b/net/compat.c
@@ -85,7 +85,7 @@ int verify_compat_iovec(struct msghdr *kern_msg, struct iovec *kern_iov,
{
int tot_len;
- if (kern_msg->msg_namelen) {
+ if (kern_msg->msg_name && kern_msg->msg_namelen) {
if (mode == VERIFY_READ) {
int err = move_addr_to_kernel(kern_msg->msg_name,
kern_msg->msg_namelen,
@@ -93,10 +93,11 @@ int verify_compat_iovec(struct msghdr *kern_msg, struct iovec *kern_iov,
if (err < 0)
return err;
}
- if (kern_msg->msg_name)
- kern_msg->msg_name = kern_address;
- } else
+ kern_msg->msg_name = kern_address;
+ } else {
kern_msg->msg_name = NULL;
+ kern_msg->msg_namelen = 0;
+ }
tot_len = iov_from_user_compat_to_kern(kern_iov,
(struct compat_iovec __user *)kern_msg->msg_iov,
diff --git a/net/core/iovec.c b/net/core/iovec.c
index b618694..a9c46ba 100644
--- a/net/core/iovec.c
+++ b/net/core/iovec.c
@@ -39,7 +39,7 @@ int verify_iovec(struct msghdr *m, struct iovec *iov, struct sockaddr_storage *a
{
int size, ct, err;
- if (m->msg_namelen) {
+ if (m->msg_name && m->msg_namelen) {
if (mode == VERIFY_READ) {
void __user *namep;
namep = (void __user __force *) m->msg_name;
@@ -48,10 +48,10 @@ int verify_iovec(struct msghdr *m, struct iovec *iov, struct sockaddr_storage *a
if (err < 0)
return err;
}
- if (m->msg_name)
- m->msg_name = address;
+ m->msg_name = address;
} else {
m->msg_name = NULL;
+ m->msg_namelen = 0;
}
size = m->msg_iovlen * sizeof(struct iovec);
--
1.9.1
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