CVE-2024-35896: netfilter: validate user input for expected length

In the Linux kernel, the following vulnerability has been resolved:

netfilter: validate user input for expected length

I got multiple syzbot reports showing old bugs exposed by BPF after commit 20f2505fb436 ("bpf: Try to avoid kzalloc in cgroup/{s,g}etsockopt")

setsockopt() @optlen argument should be taken into account before copying data.

BUG: KASAN: slab-out-of-bounds in copyfromsockptroffset include/linux/sockptr.h:49 [inline] BUG: KASAN: slab-out-of-bounds in copyfromsockptr include/linux/sockptr.h:55 [inline] BUG: KASAN: slab-out-of-bounds in doreplace net/ipv4/netfilter/iptables.c:1111 [inline] BUG: KASAN: slab-out-of-bounds in doiptsetctl+0x902/0x3dd0 net/ipv4/netfilter/iptables.c:1627 Read of size 96 at addr ffff88802cd73da0 by task syz-executor.4/7238

CPU: 1 PID: 7238 Comm: syz-executor.4 Not tainted 6.9.0-rc2-next-20240403-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024 Call Trace: <TASK> dumpstack lib/dumpstack.c:88 [inline] dumpstacklvl+0x241/0x360 lib/dumpstack.c:114 printaddressdescription mm/kasan/report.c:377 [inline] printreport+0x169/0x550 mm/kasan/report.c:488 kasanreport+0x143/0x180 mm/kasan/report.c:601 kasancheckrange+0x282/0x290 mm/kasan/generic.c:189 asanmemcpy+0x29/0x70 mm/kasan/shadow.c:105 copyfromsockptroffset include/linux/sockptr.h:49 [inline] copyfromsockptr include/linux/sockptr.h:55 [inline] doreplace net/ipv4/netfilter/iptables.c:1111 [inline] doiptsetctl+0x902/0x3dd0 net/ipv4/netfilter/iptables.c:1627 nfsetsockopt+0x295/0x2c0 net/netfilter/nfsockopt.c:101 dosocksetsockopt+0x3af/0x720 net/socket.c:2311 syssetsockopt+0x1ae/0x250 net/socket.c:2334 dosyssetsockopt net/socket.c:2343 [inline] sesyssetsockopt net/socket.c:2340 [inline] x64syssetsockopt+0xb5/0xd0 net/socket.c:2340 dosyscall64+0xfb/0x240 entrySYSCALL64afterhwframe+0x72/0x7a RIP: 0033:0x7fd22067dde9 Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fd21f9ff0c8 EFLAGS: 00000246 ORIGRAX: 0000000000000036 RAX: ffffffffffffffda RBX: 00007fd2207abf80 RCX: 00007fd22067dde9 RDX: 0000000000000040 RSI: 0000000000000000 RDI: 0000000000000003 RBP: 00007fd2206ca47a R08: 0000000000000001 R09: 0000000000000000 R10: 0000000020000880 R11: 0000000000000246 R12: 0000000000000000 R13: 000000000000000b R14: 00007fd2207abf80 R15: 00007ffd2d0170d8 </TASK>

Allocated by task 7238: kasansavestack mm/kasan/common.c:47 [inline] kasansavetrack+0x3f/0x80 mm/kasan/common.c:68 poisonkmallocredzone mm/kasan/common.c:370 [inline] kasankmalloc+0x98/0xb0 mm/kasan/common.c:387 kasankmalloc include/linux/kasan.h:211 [inline] dokmallocnode mm/slub.c:4069 [inline] kmallocnoprof+0x200/0x410 mm/slub.c:4082 kmallocnoprof include/linux/slab.h:664 [inline] cgroupbpfrunfiltersetsockopt+0xd47/0x1050 kernel/bpf/cgroup.c:1869 dosocksetsockopt+0x6b4/0x720 net/socket.c:2293 syssetsockopt+0x1ae/0x250 net/socket.c:2334 dosyssetsockopt net/socket.c:2343 [inline] sesyssetsockopt net/socket.c:2340 [inline] x64syssetsockopt+0xb5/0xd0 net/socket.c:2340 dosyscall64+0xfb/0x240 entrySYSCALL64afterhwframe+0x72/0x7a

The buggy address belongs to the object at ffff88802cd73da0 which belongs to the cache kmalloc-8 of size 8 The buggy address is located 0 bytes inside of allocated 1-byte region [ffff88802cd73da0, ffff88802cd73da1)

The buggy address belongs to the physical page: page: refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88802cd73020 pfn:0x2cd73 flags: 0xfff80000000000(node=0|zone=1|lastcpupid=0xfff) pagetype: 0xffffefff(slab) raw: 00fff80000000000 ffff888015041280 dead000000000100 dead000000000122 raw: ffff88802cd73020 000000008080007f 00000001ffffefff 00 ---truncated---

— NVD

In the Linux kernel, the following vulnerability has been resolved:

netfilter: validate user input for expected length

The Linux kernel CVE team has assigned CVE-2024-35896 to this issue.

Upstream advisory: https://lore.kernel.org/linux-cve-announce/2024051950-CVE-2024-35896-e6b5@gregkh/T

— Red Hat