CVE-2024-56643

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

dccp: Fix memory leak in dccp_feat_change_recv

If dccp_feat_push_confirm() fails after new value for SP feature was accepted without reconciliation (entry == NULL branch), memory allocated for that value with dccp_feat_clone_sp_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>] dccp_feat_clone_sp_val net/dccp/feat.c:371 [inline] [<0000000019b38405>] dccp_feat_clone_sp_val net/dccp/feat.c:367 [inline] [<0000000019b38405>] dccp_feat_change_recv net/dccp/feat.c:1145 [inline] [<0000000019b38405>] dccp_feat_parse_options+0x1196/0x2180 net/dccp/feat.c:1416 [<00000000b1f6d94a>] dccp_parse_options+0xa2a/0x1260 net/dccp/options.c:125 [<0000000030d7b621>] dccp_rcv_state_process+0x197/0x13d0 net/dccp/input.c:650 [<000000001f74c72e>] dccp_v4_do_rcv+0xf9/0x1a0 net/dccp/ipv4.c:688 [<00000000a6c24128>] sk_backlog_rcv include/net/sock.h:1041 [inline] [<00000000a6c24128>] __release_sock+0x139/0x3b0 net/core/sock.c:2570 [<00000000cf1f3a53>] release_sock+0x54/0x1b0 net/core/sock.c:3111 [<000000008422fa23>] inet_wait_for_connect net/ipv4/af_inet.c:603 [inline] [<000000008422fa23>] __inet_stream_connect+0x5d0/0xf70 net/ipv4/af_inet.c:696 [<0000000015b6f64d>] inet_stream_connect+0x53/0xa0 net/ipv4/af_inet.c:735 [<0000000010122488>] __sys_connect_file+0x15c/0x1a0 net/socket.c:1865 [<00000000b4b70023>] __sys_connect+0x165/0x1a0 net/socket.c:1882 [<00000000f4cb3815>] __do_sys_connect net/socket.c:1892 [inline] [<00000000f4cb3815>] __se_sys_connect net/socket.c:1889 [inline] [<00000000f4cb3815>] __x64_sys_connect+0x6e/0xb0 net/socket.c:1889 [<00000000e7b1e839>] do_syscall_64+0x33/0x40 arch/x86/entry/common.c:46 [<0000000055e91434>] entry_SYSCALL_64_after_hwframe+0x67/0xd1

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

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

Weakness

The product does not sufficiently track and release allocated memory after it has been used, making the memory unavailable for reallocation and reuse.

Affected Software

Potential Mitigations

• Choose a language or tool that provides automatic memory management, or makes manual memory management less error-prone.
• For example, glibc in Linux provides protection against free of invalid pointers.
• When using Xcode to target OS X or iOS, enable automatic reference counting (ARC) [REF-391].
• To help correctly and consistently manage memory when programming in C++, consider using a smart pointer class such as std::auto_ptr (defined by ISO/IEC ISO/IEC 14882:2003), std::shared_ptr and std::unique_ptr (specified by an upcoming revision of the C++ standard, informally referred to as C++ 1x), or equivalent solutions such as Boost.

References

• https://git.kernel.org/stable/c/22be4727a8f898442066bcac34f8a1ad0bc72e14
• https://git.kernel.org/stable/c/623be080ab3c13d71570bd32f7202a8efa8e2252
• https://git.kernel.org/stable/c/6ff67909ee2ffad911e3122616df41dee23ff4f6
• https://git.kernel.org/stable/c/9ee68b0f23706a77f53c832457b9384178b76421
• https://git.kernel.org/stable/c/bc3d4423def1a9412a0ae454cb4477089ab79276
• https://git.kernel.org/stable/c/c99507fff94b926fc92279c92d80f229c91cb85d
• https://git.kernel.org/stable/c/d3ec686a369fae5034303061f003cd3f94ddfd23
• https://lists.debian.org/debian-lts-announce/2025/03/msg00001.html
• https://lists.debian.org/debian-lts-announce/2025/03/msg00002.html