CVE-2024-26754

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

gtp: fix use-after-free and null-ptr-deref in gtp_genl_dump_pdp()

The gtp_net_ops pernet operations structure for the subsystem must be registered before registering the generic netlink family.

Syzkaller hit general protection fault in gtp_genl_dump_pdp bug:

general protection fault, probably for non-canonical address 0xdffffc0000000002: 0000 [#1] PREEMPT SMP KASAN NOPTI KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017] CPU: 1 PID: 5826 Comm: gtp Not tainted 6.8.0-rc3-std-def-alt1 #1 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.0-alt1 04/01/2014 RIP: 0010:gtp_genl_dump_pdp+0x1be/0x800 [gtp] Code: c6 89 c6 e8 64 e9 86 df 58 45 85 f6 0f 85 4e 04 00 00 e8 c5 ee 86 df 48 8b 54 24 18 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 <80> 3c 02 00 0f 85 de 05 00 00 48 8b 44 24 18 4c 8b 30 4c 39 f0 74 RSP: 0018:ffff888014107220 EFLAGS: 00010202 RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000 RDX: 0000000000000002 RSI: 0000000000000000 RDI: 0000000000000000 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 R13: ffff88800fcda588 R14: 0000000000000001 R15: 0000000000000000 FS: 00007f1be4eb05c0(0000) GS:ffff88806ce80000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f1be4e766cf CR3: 000000000c33e000 CR4: 0000000000750ef0 PKRU: 55555554 Call Trace: ? show_regs+0x90/0xa0 ? die_addr+0x50/0xd0 ? exc_general_protection+0x148/0x220 ? asm_exc_general_protection+0x22/0x30 ? gtp_genl_dump_pdp+0x1be/0x800 [gtp] ? __alloc_skb+0x1dd/0x350 ? __pfx___alloc_skb+0x10/0x10 genl_dumpit+0x11d/0x230 netlink_dump+0x5b9/0xce0 ? lockdep_hardirqs_on_prepare+0x253/0x430 ? __pfx_netlink_dump+0x10/0x10 ? kasan_save_track+0x10/0x40 ? __kasan_kmalloc+0x9b/0xa0 ? genl_start+0x675/0x970 __netlink_dump_start+0x6fc/0x9f0 genl_family_rcv_msg_dumpit+0x1bb/0x2d0 ? __pfx_genl_family_rcv_msg_dumpit+0x10/0x10 ? genl_op_from_small+0x2a/0x440 ? cap_capable+0x1d0/0x240 ? __pfx_genl_start+0x10/0x10 ? __pfx_genl_dumpit+0x10/0x10 ? __pfx_genl_done+0x10/0x10 ? security_capable+0x9d/0xe0

Weakness

Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code.

Affected Software

Extended Description

The use of previously-freed memory can have any number of adverse consequences, ranging from the corruption of valid data to the execution of arbitrary code, depending on the instantiation and timing of the flaw. The simplest way data corruption may occur involves the system’s reuse of the freed memory. Use-after-free errors have two common and sometimes overlapping causes:

In this scenario, the memory in question is allocated to another pointer validly at some point after it has been freed. The original pointer to the freed memory is used again and points to somewhere within the new allocation. As the data is changed, it corrupts the validly used memory; this induces undefined behavior in the process. If the newly allocated data happens to hold a class, in C++ for example, various function pointers may be scattered within the heap data. If one of these function pointers is overwritten with an address to valid shellcode, execution of arbitrary code can be achieved.

Potential Mitigations

References

• https://git.kernel.org/stable/c/136cfaca22567a03bbb3bf53a43d8cb5748b80ec
• https://git.kernel.org/stable/c/2e534fd15e5c2ca15821c897352cf0e8a3e30dca
• https://git.kernel.org/stable/c/3963f16cc7643b461271989b712329520374ad2a
• https://git.kernel.org/stable/c/5013bd54d283eda5262c9ae3bcc966d01daf8576
• https://git.kernel.org/stable/c/a576308800be28f2eaa099e7caad093b97d66e77
• https://git.kernel.org/stable/c/ba6b8b02a3314e62571a540efa96560888c5f03e
• https://git.kernel.org/stable/c/f0ecdfa679189d26aedfe24212d4e69e42c2c861
• https://git.kernel.org/stable/c/f8cbd1791900b5d96466eede8e9439a5b9ca4de7
• https://git.kernel.org/stable/c/136cfaca22567a03bbb3bf53a43d8cb5748b80ec
• https://git.kernel.org/stable/c/2e534fd15e5c2ca15821c897352cf0e8a3e30dca
• https://git.kernel.org/stable/c/3963f16cc7643b461271989b712329520374ad2a
• https://git.kernel.org/stable/c/5013bd54d283eda5262c9ae3bcc966d01daf8576
• https://git.kernel.org/stable/c/a576308800be28f2eaa099e7caad093b97d66e77
• https://git.kernel.org/stable/c/ba6b8b02a3314e62571a540efa96560888c5f03e
• https://git.kernel.org/stable/c/f0ecdfa679189d26aedfe24212d4e69e42c2c861
• https://git.kernel.org/stable/c/f8cbd1791900b5d96466eede8e9439a5b9ca4de7
• https://lists.debian.org/debian-lts-announce/2024/06/msg00017.html
• https://lists.debian.org/debian-lts-announce/2024/06/msg00020.html