CVE-2025-40237— fs/notify: call exportfs_encode_fid with s_umount
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I. Basic Information for CVE-2025-40237
Vulnerability Information
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Vulnerability Title
fs/notify: call exportfs_encode_fid with s_umount
Source: NVD (National Vulnerability Database)
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: fs/notify: call exportfs_encode_fid with s_umount Calling intotify_show_fdinfo() on fd watching an overlayfs inode, while the overlayfs is being unmounted, can lead to dereferencing NULL ptr. This issue was found by syzkaller. Race Condition Diagram: Thread 1 Thread 2 -------- -------- generic_shutdown_super() shrink_dcache_for_umount sb->s_root = NULL | | vfs_read() | inotify_fdinfo() | * inode get from mark * | show_mark_fhandle(m, inode) | exportfs_encode_fid(inode, ..) | ovl_encode_fh(inode, ..) | ovl_check_encode_origin(inode) | * deref i_sb->s_root * | | v fsnotify_sb_delete(sb) Which then leads to: [ 32.133461] Oops: general protection fault, probably for non-canonical address 0xdffffc0000000006: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN NOPTI [ 32.134438] KASAN: null-ptr-deref in range [0x0000000000000030-0x0000000000000037] [ 32.135032] CPU: 1 UID: 0 PID: 4468 Comm: systemd-coredum Not tainted 6.17.0-rc6 #22 PREEMPT(none) <snip registers, unreliable trace> [ 32.143353] Call Trace: [ 32.143732] ovl_encode_fh+0xd5/0x170 [ 32.144031] exportfs_encode_inode_fh+0x12f/0x300 [ 32.144425] show_mark_fhandle+0xbe/0x1f0 [ 32.145805] inotify_fdinfo+0x226/0x2d0 [ 32.146442] inotify_show_fdinfo+0x1c5/0x350 [ 32.147168] seq_show+0x530/0x6f0 [ 32.147449] seq_read_iter+0x503/0x12a0 [ 32.148419] seq_read+0x31f/0x410 [ 32.150714] vfs_read+0x1f0/0x9e0 [ 32.152297] ksys_read+0x125/0x240 IOW ovl_check_encode_origin derefs inode->i_sb->s_root, after it was set to NULL in the unmount path. Fix it by protecting calling exportfs_encode_fid() from show_mark_fhandle() with s_umount lock. This form of fix was suggested by Amir in [1]. [1]: https://lore.kernel.org/all/CAOQ4uxhbDwhb+2Brs1UdkoF0a3NSdBAOQPNfEHjahrgoKJpLEw@mail.gmail.com/
Source: NVD (National Vulnerability Database)
CVSS Information
N/A
Source: NVD (National Vulnerability Database)
Vulnerability Type
N/A
Source: NVD (National Vulnerability Database)
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于exportfs_encode_fid未在s_umount保护下调用，可能导致空指针解引用。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)
Affected Products
II. Public POCs for CVE-2025-40237
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Same Patch Batch · Linux · 2025-12-04 · 53 CVEs total
| CVE-2025-40229 | mm/damon/core: fix potential memory leak by cleaning ops_filter in damon_destroy_scheme | |
| CVE-2025-40214 | af_unix: Initialise scc_index in unix_add_edge(). | |
| CVE-2025-40215 | xfrm: delete x->tunnel as we delete x | |
| CVE-2025-40220 | fuse: fix livelock in synchronous file put from fuseblk workers | |
| CVE-2025-40217 | pidfs: validate extensible ioctls | |
| CVE-2025-40218 | mm/damon/vaddr: do not repeat pte_offset_map_lock() until success | |
| CVE-2025-40219 | PCI/IOV: Fix race between SR-IOV enable/disable and hotplug | |
| CVE-2025-40216 | io_uring/rsrc: don't rely on user vaddr alignment | |
| CVE-2025-40227 | mm/damon/sysfs: dealloc commit test ctx always | |
| CVE-2025-40228 | mm/damon/sysfs: catch commit test ctx alloc failure | |
| CVE-2025-40226 | firmware: arm_scmi: Account for failed debug initialization | |
| CVE-2025-40230 | mm: prevent poison consumption when splitting THP | |
| CVE-2025-40231 | vsock: fix lock inversion in vsock_assign_transport() | |
| CVE-2025-40232 | rv: Fully convert enabled_monitors to use list_head as iterator | |
| CVE-2025-40233 | ocfs2: clear extent cache after moving/defragmenting extents | |
| CVE-2025-40234 | platform/x86: alienware-wmi-wmax: Fix NULL pointer dereference in sleep handlers | |
| CVE-2025-40236 | virtio-net: zero unused hash fields | |
| CVE-2025-40235 | btrfs: directly free partially initialized fs_info in btrfs_check_leaked_roots() | |
| CVE-2025-40238 | net/mlx5: Fix IPsec cleanup over MPV device | |
| CVE-2025-40239 | net: phy: micrel: always set shared->phydev for LAN8814 |
Showing top 20 of 53 CVEs. View all on vendor page → →
IV. Related Vulnerabilities
Same product: Linux
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scsi: storvsc: Fix scheduling while atomic on PREEMPT_RT - CVE-2026-43474
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scsi: mpi3mr: Add NULL checks when resetting request and rep - CVE-2026-43472
unshare: fix unshare_fs() handling
Same vendor: Linux
- CVE-2026-43500
rxrpc: Also unshare DATA/RESPONSE packets when paged frags a - CVE-2026-43475
scsi: storvsc: Fix scheduling while atomic on PREEMPT_RT - CVE-2026-43474
fs: init flags_valid before calling vfs_fileattr_get - CVE-2026-43473
scsi: mpi3mr: Add NULL checks when resetting request and rep - CVE-2026-43472
unshare: fix unshare_fs() handling
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