CVE-2024-26636

In the Linux kernel, the following vulnerability has been resolved: llc:
make llc_ui_sendmsg() more robust against bonding changes syzbot was able
to trick llc_ui_sendmsg(), allocating an skb with no headroom, but
subsequently trying to push 14 bytes of Ethernet header [1] Like some
others, llc_ui_sendmsg() releases the socket lock before calling
sock_alloc_send_skb(). Then it acquires it again, but does not redo all the
sanity checks that were performed. This fix: - Uses LL_RESERVED_SPACE() to
reserve space. - Check all conditions again after socket lock is held
again. - Do not account Ethernet header for mtu limitation. [1] skbuff:
skb_under_panic: text:ffff800088baa334 len:1514 put:14
head:ffff0000c9c37000 data:ffff0000c9c36ff2 tail:0x5dc end:0x6c0 dev:bond0
kernel BUG at net/core/skbuff.c:193 ! Internal error: Oops - BUG:
00000000f2000800 [#1] PREEMPT SMP Modules linked in: CPU: 0 PID: 6875 Comm:
syz-executor.0 Not tainted 6.7.0-rc8-syzkaller-00101-g0802e17d9aca-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 11/17/2023 pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS
BTYPE=–) pc : skb_panic net/core/skbuff.c:189 [inline] pc :
skb_under_panic+0x13c/0x140 net/core/skbuff.c:203 lr : skb_panic
net/core/skbuff.c:189 [inline] lr : skb_under_panic+0x13c/0x140
net/core/skbuff.c:203 sp : ffff800096f97000 x29: ffff800096f97010 x28:
ffff80008cc8d668 x27: dfff800000000000 x26: ffff0000cb970c90 x25:
00000000000005dc x24: ffff0000c9c36ff2 x23: ffff0000c9c37000 x22:
00000000000005ea x21: 00000000000006c0 x20: 000000000000000e x19:
ffff800088baa334 x18: 1fffe000368261ce x17: ffff80008e4ed000 x16:
ffff80008a8310f8 x15: 0000000000000001 x14: 1ffff00012df2d58 x13:
0000000000000000 x12: 0000000000000000 x11: 0000000000000001 x10:
0000000000ff0100 x9 : e28a51f1087e8400 x8 : e28a51f1087e8400 x7 :
ffff80008028f8d0 x6 : 0000000000000000 x5 : 0000000000000001 x4 :
0000000000000001 x3 : ffff800082b78714 x2 : 0000000000000001 x1 :
0000000100000000 x0 : 0000000000000089 Call trace: skb_panic
net/core/skbuff.c:189 [inline] skb_under_panic+0x13c/0x140
net/core/skbuff.c:203 skb_push+0xf0/0x108 net/core/skbuff.c:2451
eth_header+0x44/0x1f8 net/ethernet/eth.c:83 dev_hard_header
include/linux/netdevice.h:3188 [inline] llc_mac_hdr_init+0x110/0x17c
net/llc/llc_output.c:33 llc_sap_action_send_xid_c+0x170/0x344
net/llc/llc_s_ac.c:85 llc_exec_sap_trans_actions net/llc/llc_sap.c:153
[inline] llc_sap_next_state net/llc/llc_sap.c:182 [inline]
llc_sap_state_process+0x1ec/0x774 net/llc/llc_sap.c:209
llc_build_and_send_xid_pkt+0x12c/0x1c0 net/llc/llc_sap.c:270
llc_ui_sendmsg+0x7bc/0xb1c net/llc/af_llc.c:997 sock_sendmsg_nosec
net/socket.c:730 [inline] __sock_sendmsg net/socket.c:745 [inline]
sock_sendmsg+0x194/0x274 net/socket.c:767 splice_to_socket+0x7cc/0xd58
fs/splice.c:881 do_splice_from fs/splice.c:933 [inline]
direct_splice_actor+0xe4/0x1c0 fs/splice.c:1142
splice_direct_to_actor+0x2a0/0x7e4 fs/splice.c:1088
do_splice_direct+0x20c/0x348 fs/splice.c:1194 do_sendfile+0x4bc/0xc70
fs/read_write.c:1254 __do_sys_sendfile64 fs/read_write.c:1322 [inline]
__se_sys_sendfile64 fs/read_write.c:1308 [inline]
__arm64_sys_sendfile64+0x160/0x3b4 fs/read_write.c:1308 __invoke_syscall
arch/arm64/kernel/syscall.c:37 [inline] invoke_syscall+0x98/0x2b8
arch/arm64/kernel/syscall.c:51 el0_svc_common+0x130/0x23c
arch/arm64/kernel/syscall.c:136 do_el0_svc+0x48/0x58
arch/arm64/kernel/syscall.c:155 el0_svc+0x54/0x158
arch/arm64/kernel/entry-common.c:678 el0t_64_sync_handler+0x84/0xfc
arch/arm64/kernel/entry-common.c:696 el0t_64_sync+0x190/0x194
arch/arm64/kernel/entry.S:595 Code: aa1803e6 aa1903e7 a90023f5 94792f6a
(d4210000)

Notes