{"id":"DEBIAN-CVE-2026-98507","details":"In the Linux kernel, the following vulnerability has been resolved:  mm/rmap: fix missing barrier between anon_vma init and vma-\u003eanon_vma publish  On arm64 server, we find that a task trying to grab the anon_vma lock triggers hungtask.  INFO: task main:2354726 blocked for more than 120 seconds.       Tainted: G            E     5.10.0-0021.aarch64 #1 \"echo 0 \u003e /proc/sys/kernel/hung_task_timeout_secs\" disables this message. task:main            state:D stack:    0 pid:2354726 ppid:2350673 flags:0x00000a01 Call trace:  __switch_to+0x7c/0xbc  __schedule+0x3b4/0x8a0  schedule+0x50/0xe0  rwsem_down_write_slowpath+0x3cc/0x6cc  down_write+0x60/0x260  __anon_vma_prepare+0x6c/0x210  do_anonymous_page+0x258/0x660  handle_pte_fault+0x188/0x214  __handle_mm_fault+0x1b0/0x380  handle_mm_fault+0xf4/0x284  do_page_fault+0x19c/0x494  do_translation_fault+0xcc/0xf8  do_mem_abort+0x48/0xac  el0_da+0x44/0x80  el0_sync_handler+0x88/0xb4  el0_sync+0x160/0x180  After analyzing the vmcore, we found the anon_vma-\u003eroot-\u003erwsem.count is -1.  There is another anon_vma whose anon_vma-\u003eroot-\u003erwsem.count is 1, the anon_vma-\u003eroot-\u003erwsem.owner shows the lock is held, but the stack of the task shows the task doesn't hold the anon_vma lock.  After adding more debugging info, we found __anon_vma_prepare() reuses anon_vma and triggers the UAF of anon_vma-\u003eroot due to missing memory barrier, leading to locking and unlocking two different anon_vma-\u003eroot, thus leading to an anon_vma will never be unlocked, and another anon_vma couldn't be locked anymore.  This race requires two adjacent VMAs that are not merged but are anon_vma-compatible (e.g., they differ in VMA_ACCESS_FLAGS that can be changed by mprotect()).  Two threads fault on each VMA concurrently, both calling __anon_vma_prepare() with only mmap_lock held for reading.      THREAD A                             THREAD B __anon_vma_prepare                __anon_vma_prepare  find_mergeable_anon_vma() -\u003e NULL  anon_vma = anon_vma_alloc();    anon_vma-\u003eroot = anon_vma;  // the two stores may be reordered  vma-\u003eanon_vma = anon_vma;                                    // finds A's anon_vma                                    anon_vma = find_mergeable_anon_vma(vma);                                    anon_vma_lock_write(anon_vma);                                      // may still see the old root                                      down_write(&anon_vma-\u003eroot-\u003erwsem);                                    anon_vma_unlock_write(anon_vma);                                      // see the new root, never unlock old                                      up_write(&anon_vma-\u003eroot-\u003erwsem);  thread A triggers page fault and calls __anon_vma_prepare() to prepare anon_vma for the faulting vma.  __anon_vma_prepare() allocates and initializes a new anon_vma, and then publishes it to the vma with a plain store.  anon_vma_prepare() only requires the mmap_lock to be held for reading, so two threads can fault on adjacent VMAs at the same time.  While thread A publishes a new anon_vma, thread B could find the anon_vma via find_mergeable_anon_vma() and then locks anon_vma-\u003eroot-\u003erwsem.  The store to anon_vma-\u003eroot in anon_vma_alloc() and the store to vma-\u003eanon_vma can be reordered.  The anon_vma_lock_write() and spin_lock() only provide acquire semantics, which do not prevent prior stores from being reordered after them.  The release semantics of the corresponding spin_unlock() and anon_vma_unlock_write() come too late, the store to vma-\u003eanon_vma is already published before they take effect.  As a result, thread B can observe the following order:      vma-\u003eanon_vma = anon_vma;     anon_vma-\u003eroot = anon_vma;  The anon_vma slab is SLAB_TYPESAFE_BY_RCU, so a newly allocated anon_vma may reuse memory from a previously freed one.  The constructor (anon_vma_ctor) does not reset anon_vma-\u003eroot, and __put_anon_vma() doesn't clear it either, so the old root value persists until anon_vma_alloc() overwrites it.  If that store isn't v ---truncated---","modified":"2026-10-19T05:00:21.352693042Z","published":"2026-10-18T17:47:39.856962665Z","upstream":["CVE-2026-98507"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2026-98507"}],"affected":[{"package":{"name":"linux","ecosystem":"Debian:12","purl":"pkg:deb/debian/linux?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["6.1.106-1","6.1.106-2","6.1.106-3","6.1.112-1","6.1.115-1","6.1.119-1","6.1.123-1","6.1.124-1","6.1.128-1","6.1.129-1","6.1.133-1","6.1.135-1","6.1.137-1","6.1.139-1","6.1.140-1","6.1.147-1","6.1.148-1","6.1.153-1","6.1.158-1","6.1.159-1","6.1.162-1","6.1.164-1","6.1.170-1","6.1.170-2","6.1.170-3","6.1.172-1","6.1.174-1","6.1.176-1","6.1.177-1","6.1.180-1","6.1.187-1","6.1.190-1","6.1.27-1","6.1.37-1","6.1.38-1","6.1.38-2","6.1.38-2~bpo11+1","6.1.38-3","6.1.38-4","6.1.38-4~bpo11+1","6.1.52-1","6.1.55-1","6.1.55-1~bpo11+1","6.1.64-1","6.1.66-1","6.1.67-1","6.1.69-1","6.1.69-1~bpo11+1","6.1.76-1","6.1.76-1~bpo11+1","6.1.82-1","6.1.85-1","6.1.90-1","6.1.90-1~bpo11+1","6.1.94-1","6.1.94-1~bpo11+1","6.1.98-1","6.1.99-1","6.10-1~exp1","6.10.1-1~exp1","6.10.11-1","6.10.11-1~bpo12+1","6.10.12-1","6.10.3-1","6.10.4-1","6.10.6-1","6.10.6-1~bpo12+1","6.10.7-1","6.10.9-1","6.11-1~exp1","6.11.10-1","6.11.10-1~bpo12+1","6.11.2-1","6.11.4-1","6.11.5-1","6.11.5-1~bpo12+1","6.11.6-1","6.11.7-1","6.11.9-1","6.11~rc4-1~exp1","6.11~rc5-1~exp1","6.12.10-1","6.12.100-1","6.12.101-1","6.12.105-1","6.12.107-1","6.12.11-1","6.12.11-1+alpha","6.12.11-1+alpha.1","6.12.111-1","6.12.113-1","6.12.12-1","6.12.12-1~bpo12+1","6.12.13-1","6.12.15-1","6.12.16-1","6.12.17-1","6.12.19-1","6.12.20-1","6.12.21-1","6.12.22-1","6.12.22-1~bpo12+1","6.12.25-1","6.12.27-1","6.12.27-1~bpo12+1","6.12.29-1","6.12.3-1","6.12.30-1","6.12.30-1~bpo12+1","6.12.31-1","6.12.32-1","6.12.32-1~bpo12+1","6.12.33-1","6.12.33-1~bpo12+1","6.12.35-1","6.12.35-1~bpo12+1","6.12.37-1","6.12.38-1","6.12.38-1~bpo12+1","6.12.41-1","6.12.43-1","6.12.43-1~bpo12+1","6.12.48-1","6.12.5-1","6.12.57-1","6.12.57-1~bpo12+1","6.12.6-1","6.12.63-1","6.12.63-1~bpo12+1","6.12.69-1","6.12.69-1~bpo12+1","6.12.73-1","6.12.73-1~bpo12+1","6.12.74-1","6.12.74-2","6.12.74-2~bpo12+1","6.12.8-1","6.12.85-1","6.12.85-1~bpo12+1","6.12.86-1","6.12.86-1~bpo12+1","6.12.88-1","6.12.88-1~bpo12+1","6.12.9-1","6.12.9-1+alpha","6.12.9-1~bpo12+1","6.12.90-1","6.12.90-1~bpo12+1","6.12.90-2","6.12.90-2~bpo12+1","6.12.94-1","6.12.94-1~bpo12+1","6.12.95-1","6.12.95-1~bpo12+1","6.12.96-1","6.12~rc6-1~exp1","6.13.10-1~exp1","6.13.11-1~exp1","6.13.2-1~exp1","6.13.3-1~exp1","6.13.4-1~exp1","6.13.5-1~exp1","6.13.6-1~exp1","6.13.7-1~exp1","6.13.8-1~exp1","6.13.9-1~exp1","6.13~rc6-1~exp1","6.13~rc7-1~exp1","6.14.3-1~exp1","6.14.5-1~exp1","6.14.6-1~exp1","6.15-1~exp1","6.15.1-1~exp1","6.15.2-1~exp1","6.15.3-1~exp1","6.15.4-1~exp1","6.15.5-1~exp1","6.15.6-1~exp1","6.15~rc7-1~exp1","6.16-1~exp1","6.16.1-1~exp1","6.16.10-1","6.16.11-1","6.16.12-1","6.16.12-1~bpo13+1","6.16.12-2","6.16.3-1","6.16.3-1~bpo13+1","6.16.5-1","6.16.6-1","6.16.7-1","6.16.8-1","6.16.9-1","6.16~rc7-1~exp1","6.17.10-1","6.17.11-1","6.17.12-1","6.17.13-1","6.17.13-1~bpo13+1","6.17.2-1~exp1","6.17.5-1~exp1","6.17.6-1","6.17.7-1","6.17.7-2","6.17.8-1","6.17.8-1~bpo13+1","6.17.9-1","6.18.1-1~exp1","6.18.10-1","6.18.12-1","6.18.12-1~bpo13+1","6.18.13-1","6.18.14-1","6.18.15-1","6.18.15-1~bpo13+1","6.18.2-1~exp1","6.18.3-1","6.18.5-1","6.18.5-1~bpo13+1","6.18.8-1","6.18.9-1","6.18.9-1~bpo13+1","6.18~rc4-1~exp1","6.18~rc4-1~exp2","6.18~rc5-1~exp1","6.18~rc6-1~exp1","6.18~rc7-1~exp1","6.19-1~exp1","6.19.10-1","6.19.10-1~bpo13+1","6.19.11-1","6.19.11-1~bpo13+1","6.19.12-1","6.19.13-1","6.19.13-1~bpo13+1","6.19.14-1","6.19.14-1~bpo13+1","6.19.2-1~exp1","6.19.3-1~exp1","6.19.4-1~exp1","6.19.5-1~exp1","6.19.6-1","6.19.6-2","6.19.6-2~bpo13+1","6.19.8-1","6.19.8-1~bpo13+1","6.19~rc4-1~exp1","6.19~rc5-1~exp1","6.19~rc6-1~exp1","6.19~rc7-1~exp1","6.19~rc8-1~exp1","6.3.1-1~exp1","6.3.11-1","6.3.2-1~exp1","6.3.4-1~exp1","6.3.5-1~exp1","6.3.7-1","6.3.7-1~bpo12+1","6.4.1-1~exp1","6.4.11-1","6.4.13-1","6.4.4-1","6.4.4-1~bpo12+1","6.4.4-2","6.4.4-3","6.4.4-3~bpo12+1","6.4~rc6-1~exp1","6.4~rc7-1~exp1","6.5.1-1~exp1","6.5.10-1","6.5.10-1~bpo12+1","6.5.13-1","6.5.3-1","6.5.3-1~bpo12+1","6.5.6-1","6.5.8-1","6.5~rc4-1~exp1","6.5~rc6-1~exp1","6.5~rc7-1~exp1","6.6.11-1","6.6.13-1","6.6.13-1~bpo12+1","6.6.15-1","6.6.15-2","6.6.3-1~exp1","6.6.4-1~exp1","6.6.7-1~exp1","6.6.8-1","6.6.9-1","6.7-1~exp1","6.7.1-1~exp1","6.7.12-1","6.7.12-1~bpo12+1","6.7.4-1~exp1","6.7.7-1","6.7.9-1","6.7.9-2","6.8.11-1","6.8.12-1","6.8.12-1~bpo12+1","6.8.9-1","6.9.10-1","6.9.10-1~bpo12+1","6.9.11-1","6.9.12-1","6.9.2-1~exp1","6.9.7-1","6.9.7-1~bpo12+1","6.9.8-1","6.9.9-1","7.0-1~exp1","7.0.1-1~exp1","7.0.10-1","7.0.10-1~bpo13+1","7.0.12-1","7.0.12-2","7.0.12-2~bpo13+1","7.0.13-1","7.0.13-1~bpo13+1","7.0.14-1","7.0.3-1","7.0.4-1","7.0.4-1~bpo13+1","7.0.7-1","7.0.7-1~bpo13+1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