{"id":"CVE-2026-52939","summary":"net/rds: fix NULL deref in rds_ib_send_cqe_handler() on masked atomic completion","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/rds: fix NULL deref in rds_ib_send_cqe_handler() on masked atomic completion\n\nrds_ib_xmit_atomic() always programs a masked atomic opcode\n(IB_WR_MASKED_ATOMIC_CMP_AND_SWP or IB_WR_MASKED_ATOMIC_FETCH_AND_ADD)\nfor every RDS atomic cmsg.  But the completion-side switch in\nrds_ib_send_unmap_op() only handles the non-masked opcodes, so a masked\natomic completion falls through to default and returns rm == NULL while\nsend-\u003es_op is left set.  rds_ib_send_cqe_handler() then dereferences the\nNULL rm via rm-\u003em_final_op, oopsing in softirq context.  An unprivileged\nAF_RDS sendmsg() of an atomic cmsg over an active RDS/IB connection\ntriggers it; on hardware that natively accepts masked atomics (mlx4,\nmlx5) no extra setup is needed.\n\n  RDS/IB: rds_ib_send_unmap_op: unexpected opcode 0xd in WR!\n  Oops: general protection fault [#1] SMP KASAN\n  KASAN: null-ptr-deref in range [0x0000000000000190-0x0000000000000197]\n  RIP: rds_ib_send_cqe_handler+0x25c/0xb10 (net/rds/ib_send.c:282)\n  Call Trace:\n   \u003cIRQ\u003e\n   rds_ib_send_cqe_handler (net/rds/ib_send.c:282)\n   poll_scq (net/rds/ib_cm.c:274)\n   rds_ib_tasklet_fn_send (net/rds/ib_cm.c:294)\n   tasklet_action_common (kernel/softirq.c:943)\n   handle_softirqs (kernel/softirq.c:573)\n   run_ksoftirqd (kernel/softirq.c:479)\n   \u003c/IRQ\u003e\n  Kernel panic - not syncing: Fatal exception in interrupt\n\nHandle the masked atomic opcodes in the same case as the non-masked\nones: they map to the same struct rds_message.atomic union member, so\nthe existing container_of()/rds_ib_send_unmap_atomic() body is correct\nfor them.","modified":"2026-07-10T03:54:48.507141117Z","published":"2026-06-24T07:14:28.622Z","related":["CGA-p6mr-jp48-f5w4"],"database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/52xxx/CVE-2026-52939.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/0f22412a2f4fbbe0251c132abee045d15a90e5b6"},{"type":"WEB","url":"https://git.kernel.org/stable/c/0f7baa82a24813cdad0b06a6f8f07e4824af5ed5"},{"type":"WEB","url":"https://git.kernel.org/stable/c/34080db3e70ddf94c38512ad2331e3c3afca6cc1"},{"type":"WEB","url":"https://git.kernel.org/stable/c/4dd262f875e87653df50b138de1390ab0628e6b7"},{"type":"WEB","url":"https://git.kernel.org/stable/c/4fd34669558085bcb589aa2078a13b0ca79e360d"},{"type":"WEB","url":"https://git.kernel.org/stable/c/6e4615164d185a26badb2f376a2449f4d174a5f0"},{"type":"WEB","url":"https://git.kernel.org/stable/c/a0148342badd8c9b2e46551766a27cb76c82e715"},{"type":"WEB","url":"https://git.kernel.org/stable/c/dcf458120add64c96a6ef5cf719340453f6e6abf"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/52xxx/CVE-2026-52939.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-52939"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"20c72bd5f5f902e5a8745d51573699605bf8d21c"},{"fixed":"a0148342badd8c9b2e46551766a27cb76c82e715"},{"fixed":"4dd262f875e87653df50b138de1390ab0628e6b7"},{"fixed":"6e4615164d185a26badb2f376a2449f4d174a5f0"},{"fixed":"0f22412a2f4fbbe0251c132abee045d15a90e5b6"},{"fixed":"0f7baa82a24813cdad0b06a6f8f07e4824af5ed5"},{"fixed":"dcf458120add64c96a6ef5cf719340453f6e6abf"},{"fixed":"4fd34669558085bcb589aa2078a13b0ca79e360d"},{"fixed":"34080db3e70ddf94c38512ad2331e3c3afca6cc1"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-52939.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"2.6.37"},{"fixed":"5.10.259"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.11.0"},{"fixed":"5.15.210"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.16.0"},{"fixed":"6.1.176"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.143"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.94"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.36"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.0.13"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-52939.json"}}],"schema_version":"1.7.5"}