CVE-2024-44946
Publication date:
31/08/2024
In the Linux kernel, the following vulnerability has been resolved:<br />
<br />
kcm: Serialise kcm_sendmsg() for the same socket.<br />
<br />
syzkaller reported UAF in kcm_release(). [0]<br />
<br />
The scenario is<br />
<br />
1. Thread A builds a skb with MSG_MORE and sets kcm->seq_skb.<br />
<br />
2. Thread A resumes building skb from kcm->seq_skb but is blocked<br />
by sk_stream_wait_memory()<br />
<br />
3. Thread B calls sendmsg() concurrently, finishes building kcm->seq_skb<br />
and puts the skb to the write queue<br />
<br />
4. Thread A faces an error and finally frees skb that is already in the<br />
write queue<br />
<br />
5. kcm_release() does double-free the skb in the write queue<br />
<br />
When a thread is building a MSG_MORE skb, another thread must not touch it.<br />
<br />
Let&#39;s add a per-sk mutex and serialise kcm_sendmsg().<br />
<br />
[0]:<br />
BUG: KASAN: slab-use-after-free in __skb_unlink include/linux/skbuff.h:2366 [inline]<br />
BUG: KASAN: slab-use-after-free in __skb_dequeue include/linux/skbuff.h:2385 [inline]<br />
BUG: KASAN: slab-use-after-free in __skb_queue_purge_reason include/linux/skbuff.h:3175 [inline]<br />
BUG: KASAN: slab-use-after-free in __skb_queue_purge include/linux/skbuff.h:3181 [inline]<br />
BUG: KASAN: slab-use-after-free in kcm_release+0x170/0x4c8 net/kcm/kcmsock.c:1691<br />
Read of size 8 at addr ffff0000ced0fc80 by task syz-executor329/6167<br />
<br />
CPU: 1 PID: 6167 Comm: syz-executor329 Tainted: G B 6.8.0-rc5-syzkaller-g9abbc24128bc #0<br />
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024<br />
Call trace:<br />
dump_backtrace+0x1b8/0x1e4 arch/arm64/kernel/stacktrace.c:291<br />
show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:298<br />
__dump_stack lib/dump_stack.c:88 [inline]<br />
dump_stack_lvl+0xd0/0x124 lib/dump_stack.c:106<br />
print_address_description mm/kasan/report.c:377 [inline]<br />
print_report+0x178/0x518 mm/kasan/report.c:488<br />
kasan_report+0xd8/0x138 mm/kasan/report.c:601<br />
__asan_report_load8_noabort+0x20/0x2c mm/kasan/report_generic.c:381<br />
__skb_unlink include/linux/skbuff.h:2366 [inline]<br />
__skb_dequeue include/linux/skbuff.h:2385 [inline]<br />
__skb_queue_purge_reason include/linux/skbuff.h:3175 [inline]<br />
__skb_queue_purge include/linux/skbuff.h:3181 [inline]<br />
kcm_release+0x170/0x4c8 net/kcm/kcmsock.c:1691<br />
__sock_release net/socket.c:659 [inline]<br />
sock_close+0xa4/0x1e8 net/socket.c:1421<br />
__fput+0x30c/0x738 fs/file_table.c:376<br />
____fput+0x20/0x30 fs/file_table.c:404<br />
task_work_run+0x230/0x2e0 kernel/task_work.c:180<br />
exit_task_work include/linux/task_work.h:38 [inline]<br />
do_exit+0x618/0x1f64 kernel/exit.c:871<br />
do_group_exit+0x194/0x22c kernel/exit.c:1020<br />
get_signal+0x1500/0x15ec kernel/signal.c:2893<br />
do_signal+0x23c/0x3b44 arch/arm64/kernel/signal.c:1249<br />
do_notify_resume+0x74/0x1f4 arch/arm64/kernel/entry-common.c:148<br />
exit_to_user_mode_prepare arch/arm64/kernel/entry-common.c:169 [inline]<br />
exit_to_user_mode arch/arm64/kernel/entry-common.c:178 [inline]<br />
el0_svc+0xac/0x168 arch/arm64/kernel/entry-common.c:713<br />
el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:730<br />
el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:598<br />
<br />
Allocated by task 6166:<br />
kasan_save_stack mm/kasan/common.c:47 [inline]<br />
kasan_save_track+0x40/0x78 mm/kasan/common.c:68<br />
kasan_save_alloc_info+0x70/0x84 mm/kasan/generic.c:626<br />
unpoison_slab_object mm/kasan/common.c:314 [inline]<br />
__kasan_slab_alloc+0x74/0x8c mm/kasan/common.c:340<br />
kasan_slab_alloc include/linux/kasan.h:201 [inline]<br />
slab_post_alloc_hook mm/slub.c:3813 [inline]<br />
slab_alloc_node mm/slub.c:3860 [inline]<br />
kmem_cache_alloc_node+0x204/0x4c0 mm/slub.c:3903<br />
__alloc_skb+0x19c/0x3d8 net/core/skbuff.c:641<br />
alloc_skb include/linux/skbuff.h:1296 [inline]<br />
kcm_sendmsg+0x1d3c/0x2124 net/kcm/kcmsock.c:783<br />
sock_sendmsg_nosec net/socket.c:730 [inline]<br />
__sock_sendmsg net/socket.c:745 [inline]<br />
sock_sendmsg+0x220/0x2c0 net/socket.c:768<br />
splice_to_socket+0x7cc/0xd58 fs/splice.c:889<br />
do_splice_from fs/splice.c:941 [inline]<br />
direct_splice_actor+0xec/0x1d8 fs/splice.c:1164<br />
splice_direct_to_actor+0x438/0xa0c fs/splice.c:1108<br />
do_splice_direct_actor <br />
---truncated---
Severity:
Pending analysis
Last modification:
31/08/2024