CVE-2026-64593
Full vulnerability record from the local CVENow database.
Description
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(): ASSERT(device->bdev, "devid=%llu path=%s dev_state=0x%lx\n", device->devid, btrfs_dev_name(device), device->dev_state); And it shows the following output: assertion failed: device->bdev, in extent-tree.c:6630 (devid=2 path=/dev/sdd dev_state=0x82) Which means the device->bdev 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->bdev) So the NULL pointer dereference is caused by device->bdev 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->name, name); | This updates the missing device's path to the new good path. | |- clear_bit(BTRFS_DEV_STATE_MISSING, &device->dev_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->bdev 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---
View original CVE JSON
{
"id": "CVE-2026-64593",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"published": "2026-08-06T08:16:34.730",
"lastModified": "2026-11-06T17:19:16.387",
"vulnStatus": "Received",
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: do not trim a device which is not writeable\n\n[BUG]\nThere is a bug report that btrfs/242 can randomly fail with the\nfollowing NULL pointer dereference:\n\n run fstests btrfs/242 at 2026-06-01 10:25:08\n BTRFS: device fsid d4d7f234-487c-4787-88e4-47a8b68c9874 devid 1 transid 9 /dev/sdc (8:32) scanned by mount (122609)\n BTRFS info (device sdc): first mount of filesystem d4d7f234-487c-4787-88e4-47a8b68c9874\n BTRFS info (device sdc): using crc32c checksum algorithm\n BTRFS warning (device sdc): devid 2 uuid fbe72d72-3272-482d-80fb-ab88ed398192 is missing\n BTRFS warning (device sdc): devid 2 uuid fbe72d72-3272-482d-80fb-ab88ed398192 is missing\n BTRFS info (device sdc): allowing degraded mounts\n BTRFS info (device sdc): turning on async discard\n BTRFS info (device sdc): enabling free space tree\n Unable to handle kernel NULL pointer dereference at virtual address 0000000000000018\n user pgtable: 4k pages, 48-bit VAs, pgdp=000000013fd6b000\n CPU: 4 UID: 0 PID: 122625 Comm: fstrim Not tainted 7.0.10-2-default #1 PREEMPT(full) openSUSE Tumbleweed e9a5f6b24978fba3bf015a992f865837fdfff3dd\n Hardware name: QEMU KVM Virtual Machine, BIOS edk2-20250812-19.fc42 08/12/2025\n pstate: 01400005 (nzcv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--)\n pc : btrfs_trim_fs+0x34c/0xa00 [btrfs]\n lr : btrfs_trim_fs+0x1f0/0xa00 [btrfs]\n Call trace:\n btrfs_trim_fs+0x34c/0xa00 [btrfs f02c1d570ceea621c69d302ba75dd61868083840] (P)\n btrfs_ioctl_fitrim+0xe8/0x178 [btrfs f02c1d570ceea621c69d302ba75dd61868083840]\n btrfs_ioctl+0xdd4/0x2bd8 [btrfs f02c1d570ceea621c69d302ba75dd61868083840]\n __arm64_sys_ioctl+0xac/0x108\n invoke_syscall.constprop.0+0x5c/0xd0\n el0_svc_common.constprop.0+0x40/0xf0\n do_el0_svc+0x24/0x40\n el0_svc+0x40/0x1d0\n el0t_64_sync_handler+0xa0/0xe8\n el0t_64_sync+0x1b0/0x1b8\n Code: 17ffff83 f94017e0 f9002be0 f9402ea0 (f9400c00)\n ---[ end trace 0000000000000000 ]---\n\nAlso the reporter is very kind to test the following ASSERT() added to\nbtrfs_trim_free_extents_throttle():\n\n\tASSERT(device->bdev,\n\t \"devid=%llu path=%s dev_state=0x%lx\\n\",\n\t device->devid, btrfs_dev_name(device), device->dev_state);\n\nAnd it shows the following output:\n\n assertion failed: device->bdev, in extent-tree.c:6630 (devid=2 path=/dev/sdd dev_state=0x82)\n\nWhich means the device->bdev is NULL, and the dev_state is\nBTRFS_DEV_STATE_IN_FS_METADATA | BTRFS_DEV_STATE_ITEM_FOUND, without\nBTRFS_DEV_STATE_WRITEABLE flag set.\n\n[CAUSE]\nThe pc points to the following call chain:\n\n btrfs_trim_fs()\n |- btrfs_trim_free_extents()\n |- btrfs_trim_free_extents_throttle()\n |- bdev_max_discard_sectors(device->bdev)\n\nSo the NULL pointer dereference is caused by device->bdev being NULL.\n\nThis looks impossible by a quick glance, as just before calling\nbtrfs_trim_free_extents_throttle(), we have skipped any device that has\nBTRFS_DEV_STATE_MISSING flag set.\n\nHowever in this particular case, there is a window where the missing\ndevice is later re-scanned, causing btrfs to remove the\nBTRFS_DEV_STATE_MISSING flag:\n\n btrfs_control_ioctl()\n |- btrfs_scan_one_device()\n |- device_list_add()\n |- rcu_assign_pointer(device->name, name);\n | This updates the missing device's path to the new good path.\n |\n |- clear_bit(BTRFS_DEV_STATE_MISSING, &device->dev_state)\n This removes the BTRFS_DEV_STATE_MISSING flag.\n\nThis allows the missing device to re-appear and clear the\nBTRFS_DEV_STATE_MISSING flag. However the device still does not have\nthe BTRFS_DEV_STATE_WRITEABLE flag set, nor is its bdev pointer updated.\n\nThe bdev pointer remains NULL, triggering the crash later.\n\n[FIX]\nThis is a big de-synchronization between BTRFS_DEV_STATE_MISSING and\ndevice->bdev pointer, and shows a gap in btrfs's re-appearing-device\nhandling.\n\nThe proper handling of re-appearing device will need quite some extra\nwork, which is out of the context of this small\n---truncated---"
}
],
"affected": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
{
"vendor": "Linux",
"product": "Linux",
"defaultStatus": "unaffected",
"programFiles": [
"fs/btrfs/extent-tree.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"versions": [
{
"version": "499f377f49f085ee4aa214c738e948e88626f39b",
"lessThan": "f41ae7e6664f3c4361129728f2c4d5f3ed995251",
"versionType": "git",
"status": "affected"
},
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"status": "affected"
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{
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}
]
},
{
"vendor": "Linux",
"product": "Linux",
"defaultStatus": "affected",
"programFiles": [
"fs/btrfs/extent-tree.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"versions": [
{
"version": "4.3",
"status": "affected"
},
{
"version": "0",
"lessThan": "4.3",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "5.10.261",
"lessThanOrEqual": "5.10.*",
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},
{
"version": "5.15.212",
"lessThanOrEqual": "5.15.*",
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"status": "unaffected"
},
{
"version": "6.1.178",
"lessThanOrEqual": "6.1.*",
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"status": "unaffected"
},
{
"version": "6.6.145",
"lessThanOrEqual": "6.6.*",
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"status": "unaffected"
},
{
"version": "6.12.96",
"lessThanOrEqual": "6.12.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.18.39",
"lessThanOrEqual": "6.18.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "7.1.4",
"lessThanOrEqual": "7.1.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "7.2",
"lessThanOrEqual": "*",
"versionType": "original_commit_for_fix",
"status": "unaffected"
}
]
}
]
}
],
"metrics": {
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"timestamp": "2026-11-06T16:41:58.546427Z",
"id": "CVE-2026-64593",
"options": [
{
"exploitation": "none"
},
{
"automatable": "no"
},
{
"technicalImpact": "partial"
}
],
"role": "CISA Coordinator",
"version": "2.0.3"
}
}
]
},
"references": [
{
"url": "https://git.kernel.org/stable/c/02c903fc6fc7e16c5d1f22d18784f1208acf43e3",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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{
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{
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{
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}