Description
In the Linux kernel, the following vulnerability has been resolved: atm: lec: fix null-ptr-deref in lec_arp_clear_vccs syzkaller reported a null-ptr-deref in lec_arp_clear_vccs(). This issue can be easily reproduced using the syzkaller reproducer. In the ATM LANE (LAN Emulation) module, the same atm_vcc can be shared by multiple lec_arp_table entries (e.g., via entry->vcc or entry->recv_vcc). When the underlying VCC is closed, lec_vcc_close() iterates over all ARP entries and calls lec_arp_clear_vccs() for each matched entry. For example, when lec_vcc_close() iterates through the hlists in priv->lec_arp_empty_ones or other ARP tables: 1. In the first iteration, for the first matched ARP entry sharing the VCC, lec_arp_clear_vccs() frees the associated vpriv (which is vcc->user_back) and sets vcc->user_back to NULL. 2. In the second iteration, for the next matched ARP entry sharing the same VCC, lec_arp_clear_vccs() is called again. It obtains a NULL vpriv from vcc->user_back (via LEC_VCC_PRIV(vcc)) and then attempts to dereference it via `vcc->pop = vpriv->old_pop`, leading to a null-ptr-deref crash. Fix this by adding a null check for vpriv before dereferencing it. If vpriv is already NULL, it means the VCC has been cleared by a previous call, so we can safely skip the cleanup and just clear the entry's vcc/recv_vcc pointers. The entire cleanup block (including vcc_release_async()) is placed inside the vpriv guard because a NULL vpriv indicates the VCC has already been fully released by a prior iteration — repeating the teardown would redundantly set flags and trigger callbacks on an already-closing socket. The Fixes tag points to the initial commit because the entry->vcc path has been vulnerable since the original code. The entry->recv_vcc path was later added by commit 8d9f73c0ad2f ("atm: fix a memory leak of vcc->user_back") with the same pattern, and both paths are fixed here.
Affected products
Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.
Linux Linux
Default version status: unaffected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to < 8aff65a82b6389ec674d46e5b3d3ae6f07db5e3eaffected1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to < 30c9744a989feb22cfbb84170eb0e038a7a2c1daaffected1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to < e9665986eb127290ceb535bd5d04d7a84265d94faffected1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to < 622062f24644b4536d3f437e0cf7a8c4bb421665affected1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to < 2d9f57ea29a1f1772373b98a509b44d49fda609eaffected1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to < 7ea92ab075d809ec8a96669a5ecf00f752057875affected1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to < 5f1cfea7921f5c126a441d973690eeba52677b64affected1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to < 101bacb303e89dc2e0640ae6a5e0fb97c4eb45bbaffected
Linux Linux
Default version status: affected
2.6.12affected0 to < 2.6.12unaffected5.10.253 to ≤ 5.10.*unaffected5.15.203 to ≤ 5.15.*unaffected6.1.167 to ≤ 6.1.*unaffected6.6.130 to ≤ 6.6.*unaffected6.12.77 to ≤ 6.12.*unaffected6.18.17 to ≤ 6.18.*unaffected6.19.7 to ≤ 6.19.*unaffected7.0 to ≤ *unaffected
References
- https://git.kernel.org/stable/c/8aff65a82b6389ec674d46e5b3d3ae6f07db5e3e ↗
- https://git.kernel.org/stable/c/30c9744a989feb22cfbb84170eb0e038a7a2c1da ↗
- https://git.kernel.org/stable/c/e9665986eb127290ceb535bd5d04d7a84265d94f ↗
- https://git.kernel.org/stable/c/622062f24644b4536d3f437e0cf7a8c4bb421665 ↗
- https://git.kernel.org/stable/c/2d9f57ea29a1f1772373b98a509b44d49fda609e ↗
- https://git.kernel.org/stable/c/7ea92ab075d809ec8a96669a5ecf00f752057875 ↗
- https://git.kernel.org/stable/c/5f1cfea7921f5c126a441d973690eeba52677b64 ↗
- https://git.kernel.org/stable/c/101bacb303e89dc2e0640ae6a5e0fb97c4eb45bb ↗