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

net: do not leave a dangling sk pointer, when socket creation fails

It is possible to trigger a use-after-free by: * attaching an fentry probe to _sockrelease() and the probe calling the bpfgetsocket_cookie() helper * running traceroute -I 1.1.1.1 on a freshly booted VM

A KASAN enabled kernel will log something like below (decoded and stripped):

BUG: KASAN: slab-use-after-free in _sockgencookie (./arch/x86/include/asm/atomic6464.h:15 ./include/linux/atomic/atomic-arch-fallback.h:2583 ./include/linux/atomic/atomic-instrumented.h:1611 net/core/sock_diag.c:29) Read of size 8 at addr ffff888007110dd8 by task traceroute/299

CPU: 2 PID: 299 Comm: traceroute Tainted: G E 6.10.0-rc2+ #2 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-debian-1.16.2-1 04/01/2014 Call Trace: <TASK> dumpstacklvl (lib/dumpstack.c:117 (discriminator 1)) printreport (mm/kasan/report.c:378 mm/kasan/report.c:488) ? sockgencookie (./arch/x86/include/asm/atomic6464.h:15 ./include/linux/atomic/atomic-arch-fallback.h:2583 ./include/linux/atomic/atomic-instrumented.h:1611 net/core/sockdiag.c:29) kasanreport (mm/kasan/report.c:603) ? _sockgencookie (./arch/x86/include/asm/atomic6464.h:15 ./include/linux/atomic/atomic-arch-fallback.h:2583 ./include/linux/atomic/atomic-instrumented.h:1611 net/core/sockdiag.c:29) kasancheckrange (mm/kasan/generic.c:183 mm/kasan/generic.c:189) _sockgencookie (./arch/x86/include/asm/atomic6464.h:15 ./include/linux/atomic/atomic-arch-fallback.h:2583 ./include/linux/atomic/atomic-instrumented.h:1611 net/core/sockdiag.c:29) bpfgetsocketptrcookie (./arch/x86/include/asm/preempt.h:94 ./include/linux/sockdiag.h:42 net/core/filter.c:5094 net/core/filter.c:5092) bpfprog875642cf11f1d139sockrelease+0x6e/0x8e bpftrampoline6442506592+0x47/0xaf _sockrelease (net/socket.c:652) _sockcreate (net/socket.c:1601) ... Allocated by task 299 on cpu 2 at 78.328492s: kasansavestack (mm/kasan/common.c:48) kasansavetrack (mm/kasan/common.c:68) _kasanslaballoc (mm/kasan/common.c:312 mm/kasan/common.c:338) kmemcacheallocnoprof (mm/slub.c:3941 mm/slub.c:4000 mm/slub.c:4007) skprotalloc (net/core/sock.c:2075) skalloc (net/core/sock.c:2134) inetcreate (net/ipv4/afinet.c:327 net/ipv4/afinet.c:252) _sockcreate (net/socket.c:1572) _syssocket (net/socket.c:1660 net/socket.c:1644 net/socket.c:1706) _x64syssocket (net/socket.c:1718) dosyscall64 (arch/x86/entry/common.c:52 arch/x86/entry/common.c:83) entrySYSCALL64afterhwframe (arch/x86/entry/entry64.S:130)

Freed by task 299 on cpu 2 at 78.328502s: kasansavestack (mm/kasan/common.c:48) kasansavetrack (mm/kasan/common.c:68) kasansavefreeinfo (mm/kasan/generic.c:582) poisonslabobject (mm/kasan/common.c:242) _kasanslabfree (mm/kasan/common.c:256) kmemcachefree (mm/slub.c:4437 mm/slub.c:4511) _skdestruct (net/core/sock.c:2117 net/core/sock.c:2208) inetcreate (net/ipv4/afinet.c:397 net/ipv4/afinet.c:252) _sockcreate (net/socket.c:1572) _syssocket (net/socket.c:1660 net/socket.c:1644 net/socket.c:1706) _x64syssocket (net/socket.c:1718) dosyscall64 (arch/x86/entry/common.c:52 arch/x86/entry/common.c:83) entrySYSCALL64afterhwframe (arch/x86/entry/entry_64.S:130)

Fix this by clearing the struct socket reference in skcommonrelease() to cover all protocol families create functions, which may already attached the reference to the sk object with sockinitdata().