CVE-2024-56643

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

dccp: Fix memory leak in dccpfeatchange_recv

If dccpfeatpushconfirm() fails after new value for SP feature was accepted without reconciliation ('entry == NULL' branch), memory allocated for that value with dccpfeatclonesp_val() is never freed.

Here is the kmemleak stack for this:

unreferenced object 0xffff88801d4ab488 (size 8): comm "syz-executor310", pid 1127, jiffies 4295085598 (age 41.666s) hex dump (first 8 bytes): 01 b4 4a 1d 80 88 ff ff ..J..... backtrace: [<00000000db7cabfe>] kmemdup+0x23/0x50 mm/util.c:128 [<0000000019b38405>] kmemdup include/linux/string.h:465 [inline] [<0000000019b38405>] dccpfeatclonespval net/dccp/feat.c:371 [inline] [<0000000019b38405>] dccpfeatclonespval net/dccp/feat.c:367 [inline] [<0000000019b38405>] dccpfeatchangerecv net/dccp/feat.c:1145 [inline] [<0000000019b38405>] dccpfeatparseoptions+0x1196/0x2180 net/dccp/feat.c:1416 [<00000000b1f6d94a>] dccpparseoptions+0xa2a/0x1260 net/dccp/options.c:125 [<0000000030d7b621>] dccprcvstateprocess+0x197/0x13d0 net/dccp/input.c:650 [<000000001f74c72e>] dccpv4dorcv+0xf9/0x1a0 net/dccp/ipv4.c:688 [<00000000a6c24128>] skbacklogrcv include/net/sock.h:1041 [inline] [<00000000a6c24128>] __releasesock+0x139/0x3b0 net/core/sock.c:2570 [<00000000cf1f3a53>] releasesock+0x54/0x1b0 net/core/sock.c:3111 [<000000008422fa23>] inetwaitforconnect net/ipv4/afinet.c:603 [inline] [<000000008422fa23>] __inetstreamconnect+0x5d0/0xf70 net/ipv4/afinet.c:696 [<0000000015b6f64d>] inetstreamconnect+0x53/0xa0 net/ipv4/afinet.c:735 [<0000000010122488>] __sysconnectfile+0x15c/0x1a0 net/socket.c:1865 [<00000000b4b70023>] __sys_connect+0x165/0x1a0 net/socket.c:1882 [<00000000f4cb3815>] __dosysconnect net/socket.c:1892 [inline] [<00000000f4cb3815>] __sesysconnect net/socket.c:1889 [inline] [<00000000f4cb3815>] __x64sysconnect+0x6e/0xb0 net/socket.c:1889 [<00000000e7b1e839>] dosyscall64+0x33/0x40 arch/x86/entry/common.c:46 [<0000000055e91434>] entrySYSCALL64afterhwframe+0x67/0xd1

Clean up the allocated memory in case of dccpfeatpush_confirm() failure and bail out with an error reset code.

Found by Linux Verification Center (linuxtesting.org) with Syzkaller.