{"id":"DEBIAN-CVE-2026-64593","details":"In the Linux kernel, the following vulnerability has been resolved:  btrfs: do not trim a device which is not writeable  [BUG] There is a bug report that btrfs/242 can randomly fail with the following NULL pointer dereference:    run fstests btrfs/242 at 2026-06-01 10:25:08   BTRFS: device fsid d4d7f234-487c-4787-88e4-47a8b68c9874 devid 1 transid 9 /dev/sdc (8:32) scanned by mount (122609)   BTRFS info (device sdc): first mount of filesystem d4d7f234-487c-4787-88e4-47a8b68c9874   BTRFS info (device sdc): using crc32c checksum algorithm   BTRFS warning (device sdc): devid 2 uuid fbe72d72-3272-482d-80fb-ab88ed398192 is missing   BTRFS warning (device sdc): devid 2 uuid fbe72d72-3272-482d-80fb-ab88ed398192 is missing   BTRFS info (device sdc): allowing degraded mounts   BTRFS info (device sdc): turning on async discard   BTRFS info (device sdc): enabling free space tree   Unable to handle kernel NULL pointer dereference at virtual address 0000000000000018   user pgtable: 4k pages, 48-bit VAs, pgdp=000000013fd6b000   CPU: 4 UID: 0 PID: 122625 Comm: fstrim Not tainted 7.0.10-2-default #1 PREEMPT(full) openSUSE Tumbleweed e9a5f6b24978fba3bf015a992f865837fdfff3dd   Hardware name: QEMU KVM Virtual Machine, BIOS edk2-20250812-19.fc42 08/12/2025   pstate: 01400005 (nzcv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--)   pc : btrfs_trim_fs+0x34c/0xa00 [btrfs]   lr : btrfs_trim_fs+0x1f0/0xa00 [btrfs]   Call trace:    btrfs_trim_fs+0x34c/0xa00 [btrfs f02c1d570ceea621c69d302ba75dd61868083840] (P)    btrfs_ioctl_fitrim+0xe8/0x178 [btrfs f02c1d570ceea621c69d302ba75dd61868083840]    btrfs_ioctl+0xdd4/0x2bd8 [btrfs f02c1d570ceea621c69d302ba75dd61868083840]    __arm64_sys_ioctl+0xac/0x108    invoke_syscall.constprop.0+0x5c/0xd0    el0_svc_common.constprop.0+0x40/0xf0    do_el0_svc+0x24/0x40    el0_svc+0x40/0x1d0    el0t_64_sync_handler+0xa0/0xe8    el0t_64_sync+0x1b0/0x1b8   Code: 17ffff83 f94017e0 f9002be0 f9402ea0 (f9400c00)   ---[ end trace 0000000000000000  ]---  Also the reporter is very kind to test the following ASSERT() added to btrfs_trim_free_extents_throttle():  \tASSERT(device-\u003ebdev, \t       \"devid=%llu path=%s dev_state=0x%lx\\n\", \t       device-\u003edevid, btrfs_dev_name(device), device-\u003edev_state);  And it shows the following output:    assertion failed: device-\u003ebdev, in extent-tree.c:6630 (devid=2 path=/dev/sdd dev_state=0x82)  Which means the device-\u003ebdev is NULL, and the dev_state is BTRFS_DEV_STATE_IN_FS_METADATA | BTRFS_DEV_STATE_ITEM_FOUND, without BTRFS_DEV_STATE_WRITEABLE flag set.  [CAUSE] The pc points to the following call chain:    btrfs_trim_fs()   |- btrfs_trim_free_extents()      |- btrfs_trim_free_extents_throttle()         |- bdev_max_discard_sectors(device-\u003ebdev)  So the NULL pointer dereference is caused by device-\u003ebdev being NULL.  This looks impossible by a quick glance, as just before calling btrfs_trim_free_extents_throttle(), we have skipped any device that has BTRFS_DEV_STATE_MISSING flag set.  However in this particular case, there is a window where the missing device is later re-scanned, causing btrfs to remove the BTRFS_DEV_STATE_MISSING flag:    btrfs_control_ioctl()   |- btrfs_scan_one_device()      |- device_list_add()         |- rcu_assign_pointer(device-\u003ename, name);         |  This updates the missing device's path to the new good path.         |         |- clear_bit(BTRFS_DEV_STATE_MISSING, &device-\u003edev_state)            This removes the BTRFS_DEV_STATE_MISSING flag.  This allows the missing device to re-appear and clear the BTRFS_DEV_STATE_MISSING flag.  However the device still does not have the BTRFS_DEV_STATE_WRITEABLE flag set, nor is its bdev pointer updated.  The bdev pointer remains NULL, triggering the crash later.  [FIX] This is a big de-synchronization between BTRFS_DEV_STATE_MISSING and device-\u003ebdev pointer, and shows a gap in btrfs's re-appearing-device handling.  The proper handling of re-appearing device will need quite some extra work, which is out of the context of this small ---truncated---","modified":"2026-09-01T16:06:56.531795818Z","published":"2026-08-06T08:16:34.730Z","upstream":["CVE-2026-64593"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2026-64593"}],"affected":[{"package":{"name":"linux","ecosystem":"Debian:12","purl":"pkg:deb/debian/linux?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.1.180-1"}]}],"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","6.1.27-1","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"],"ecosystem_specific":{"urgency":"not 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