CVE-2024-44987: ipv6: prevent UAF in ip6_send_skb()

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

ipv6: prevent UAF in ip6sendskb()

syzbot reported an UAF in ip6sendskb() [1]

After ip6localout() has returned, we no longer can safely dereference rt, unless we hold rcureadlock().

A similar issue has been fixed in commit a688caa34beb ("ipv6: take rcu lock in rawv6sendhdrinc()")

Another potential issue in ip6finishoutput2() is handled in a separate patch.

[1] BUG: KASAN: slab-use-after-free in ip6sendskb+0x18d/0x230 net/ipv6/ip6output.c:1964 Read of size 8 at addr ffff88806dde4858 by task syz.1.380/6530

CPU: 1 UID: 0 PID: 6530 Comm: syz.1.380 Not tainted 6.11.0-rc3-syzkaller-00306-gdf6cbc62cc9b #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024 Call Trace: <TASK> dumpstack lib/dumpstack.c:93 [inline] dumpstacklvl+0x241/0x360 lib/dumpstack.c:119 printaddressdescription mm/kasan/report.c:377 [inline] printreport+0x169/0x550 mm/kasan/report.c:488 kasanreport+0x143/0x180 mm/kasan/report.c:601 ip6sendskb+0x18d/0x230 net/ipv6/ip6output.c:1964 rawv6pushpendingframes+0x75c/0x9e0 net/ipv6/raw.c:588 rawv6sendmsg+0x19c7/0x23c0 net/ipv6/raw.c:926 socksendmsgnosec net/socket.c:730 [inline] socksendmsg+0x1a6/0x270 net/socket.c:745 sockwriteiter+0x2dd/0x400 net/socket.c:1160 doiterreadvwritev+0x60a/0x890 vfswritev+0x37c/0xbb0 fs/readwrite.c:971 dowritev+0x1b1/0x350 fs/readwrite.c:1018 dosyscallx64 arch/x86/entry/common.c:52 [inline] dosyscall64+0xf3/0x230 arch/x86/entry/common.c:83 entrySYSCALL64afterhwframe+0x77/0x7f RIP: 0033:0x7f936bf79e79 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f936cd7f038 EFLAGS: 00000246 ORIGRAX: 0000000000000014 RAX: ffffffffffffffda RBX: 00007f936c115f80 RCX: 00007f936bf79e79 RDX: 0000000000000001 RSI: 0000000020000040 RDI: 0000000000000004 RBP: 00007f936bfe7916 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00007f936c115f80 R15: 00007fff2860a7a8 </TASK>

Allocated by task 6530: kasansavestack mm/kasan/common.c:47 [inline] kasansavetrack+0x3f/0x80 mm/kasan/common.c:68 unpoisonslabobject mm/kasan/common.c:312 [inline] kasanslaballoc+0x66/0x80 mm/kasan/common.c:338 kasanslaballoc include/linux/kasan.h:201 [inline] slabpostallochook mm/slub.c:3988 [inline] slaballocnode mm/slub.c:4037 [inline] kmemcacheallocnoprof+0x135/0x2a0 mm/slub.c:4044 dstalloc+0x12b/0x190 net/core/dst.c:89 ip6blackholeroute+0x59/0x340 net/ipv6/route.c:2670 makeblackhole net/xfrm/xfrmpolicy.c:3120 [inline] xfrmlookuproute+0xd1/0x1c0 net/xfrm/xfrmpolicy.c:3313 ip6dstlookupflow+0x13e/0x180 net/ipv6/ip6output.c:1257 rawv6sendmsg+0x1283/0x23c0 net/ipv6/raw.c:898 socksendmsgnosec net/socket.c:730 [inline] socksendmsg+0x1a6/0x270 net/socket.c:745 syssendmsg+0x525/0x7d0 net/socket.c:2597 syssendmsg net/socket.c:2651 [inline] syssendmsg+0x2b0/0x3a0 net/socket.c:2680 dosyscallx64 arch/x86/entry/common.c:52 [inline] dosyscall64+0xf3/0x230 arch/x86/entry/common.c:83 entrySYSCALL64afterhwframe+0x77/0x7f

Freed by task 45: kasansavestack mm/kasan/common.c:47 [inline] kasansavetrack+0x3f/0x80 mm/kasan/common.c:68 kasansavefreeinfo+0x40/0x50 mm/kasan/generic.c:579 poisonslabobject+0xe0/0x150 mm/kasan/common.c:240 kasanslabfree+0x37/0x60 mm/kasan/common.c:256 kasanslabfree include/linux/kasan.h:184 [inline] slabfreehook mm/slub.c:2252 [inline] slabfree mm/slub.c:4473 [inline] kmemcachefree+0x145/0x350 mm/slub.c:4548 dstdestroy+0x2ac/0x460 net/core/dst.c:124 rcudobatch kernel/rcu/tree.c:2569 [inline] rcucore+0xafd/0x1830 kernel/rcu/tree. ---truncated---

— NVD

This CVE was automatically created from a reference found in an email or other text. If you are reading this, then this CVE entry is probably erroneous, since this text should be replaced by the official CVE description automatically.

— Launchpad