Description
In the Linux kernel, the following vulnerability has been resolved:
fuse: check for NULL root inode in fuse_fill_super_submount
fuse_iget() can return NULL when its inode allocation fails, but
fuse_fill_super_submount() passed the result straight to get_fuse_inode()
and decremented fi->nlookup without checking it:
root = fuse_iget(sb, parent_fi->nodeid, ...);
fi = get_fuse_inode(root);
fi->nlookup--;
Inside fuse_iget() the inode allocation can fail and return NULL. The
submount root takes the iget5_locked() path, whose alloc_inode() can fail
under memory pressure (the auto-submount branch can fail the same way in
new_inode() or fuse_alloc_submount_lookup()):
inode = iget5_locked(sb, nodeid, fuse_inode_eq, fuse_inode_set,
&nodeid);
if (!inode)
return NULL;
A NULL root makes get_fuse_inode() a container_of() on NULL and the
nlookup decrement a write to a bogus address, oopsing the mount. With
CONFIG_KASAN the following null pointer dereference is reported when the
root inode allocation of an auto-submount fails (e.g. under memory
pressure):
==================================================================
BUG: KASAN: null-ptr-deref in fuse_get_tree_submount+0x656/0x8b0
Read of size 8 at addr 00000000000002b0 by task ls/942
CPU: 0 PID: 942 Comm: ls Tainted: G W 6.6 #15
Call Trace:
<TASK>
fuse_get_tree_submount+0x656/0x8b0
vfs_get_tree+0x48/0x140
fc_mount+0x13/0x50
fuse_dentry_automount+0x7a/0xb0
__traverse_mounts+0xca/0x330
step_into+0x339/0xac0
path_lookupat+0xc5/0x2f0
filename_lookup+0x163/0x2a0
vfs_statx+0xd5/0x200
do_statx+0x83/0xd0
__x64_sys_statx+0xa0/0xc0
do_syscall_64+0x37/0x90
entry_SYSCALL_64_after_hwframe+0x78/0xe2
</TASK>
==================================================================
Return -ENOMEM instead; the caller tears down the partially built
superblock on error, matching the other error returns in this
function.
fuse: check for NULL root inode in fuse_fill_super_submount
fuse_iget() can return NULL when its inode allocation fails, but
fuse_fill_super_submount() passed the result straight to get_fuse_inode()
and decremented fi->nlookup without checking it:
root = fuse_iget(sb, parent_fi->nodeid, ...);
fi = get_fuse_inode(root);
fi->nlookup--;
Inside fuse_iget() the inode allocation can fail and return NULL. The
submount root takes the iget5_locked() path, whose alloc_inode() can fail
under memory pressure (the auto-submount branch can fail the same way in
new_inode() or fuse_alloc_submount_lookup()):
inode = iget5_locked(sb, nodeid, fuse_inode_eq, fuse_inode_set,
&nodeid);
if (!inode)
return NULL;
A NULL root makes get_fuse_inode() a container_of() on NULL and the
nlookup decrement a write to a bogus address, oopsing the mount. With
CONFIG_KASAN the following null pointer dereference is reported when the
root inode allocation of an auto-submount fails (e.g. under memory
pressure):
==================================================================
BUG: KASAN: null-ptr-deref in fuse_get_tree_submount+0x656/0x8b0
Read of size 8 at addr 00000000000002b0 by task ls/942
CPU: 0 PID: 942 Comm: ls Tainted: G W 6.6 #15
Call Trace:
<TASK>
fuse_get_tree_submount+0x656/0x8b0
vfs_get_tree+0x48/0x140
fc_mount+0x13/0x50
fuse_dentry_automount+0x7a/0xb0
__traverse_mounts+0xca/0x330
step_into+0x339/0xac0
path_lookupat+0xc5/0x2f0
filename_lookup+0x163/0x2a0
vfs_statx+0xd5/0x200
do_statx+0x83/0xd0
__x64_sys_statx+0xa0/0xc0
do_syscall_64+0x37/0x90
entry_SYSCALL_64_after_hwframe+0x78/0xe2
</TASK>
==================================================================
Return -ENOMEM instead; the caller tears down the partially built
superblock on error, matching the other error returns in this
function.
Published:
2026-09-17
Score:
n/a
EPSS:
n/a
KEV:
No
Impact:
n/a
Action:
n/a
Analysis
No analysis available yet.
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | ||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux | unaffected |
|
||||||||||||||||||||||||
| Linux | Linux | affected |
|
No data.
No data.
No data available yet.
Remediation
No remediation available yet.
Tracking
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Advisories
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References
History
Thu, 17 Sep 2026 16:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: fuse: check for NULL root inode in fuse_fill_super_submount fuse_iget() can return NULL when its inode allocation fails, but fuse_fill_super_submount() passed the result straight to get_fuse_inode() and decremented fi->nlookup without checking it: root = fuse_iget(sb, parent_fi->nodeid, ...); fi = get_fuse_inode(root); fi->nlookup--; Inside fuse_iget() the inode allocation can fail and return NULL. The submount root takes the iget5_locked() path, whose alloc_inode() can fail under memory pressure (the auto-submount branch can fail the same way in new_inode() or fuse_alloc_submount_lookup()): inode = iget5_locked(sb, nodeid, fuse_inode_eq, fuse_inode_set, &nodeid); if (!inode) return NULL; A NULL root makes get_fuse_inode() a container_of() on NULL and the nlookup decrement a write to a bogus address, oopsing the mount. With CONFIG_KASAN the following null pointer dereference is reported when the root inode allocation of an auto-submount fails (e.g. under memory pressure): ================================================================== BUG: KASAN: null-ptr-deref in fuse_get_tree_submount+0x656/0x8b0 Read of size 8 at addr 00000000000002b0 by task ls/942 CPU: 0 PID: 942 Comm: ls Tainted: G W 6.6 #15 Call Trace: <TASK> fuse_get_tree_submount+0x656/0x8b0 vfs_get_tree+0x48/0x140 fc_mount+0x13/0x50 fuse_dentry_automount+0x7a/0xb0 __traverse_mounts+0xca/0x330 step_into+0x339/0xac0 path_lookupat+0xc5/0x2f0 filename_lookup+0x163/0x2a0 vfs_statx+0xd5/0x200 do_statx+0x83/0xd0 __x64_sys_statx+0xa0/0xc0 do_syscall_64+0x37/0x90 entry_SYSCALL_64_after_hwframe+0x78/0xe2 </TASK> ================================================================== Return -ENOMEM instead; the caller tears down the partially built superblock on error, matching the other error returns in this function. | |
| Title | fuse: check for NULL root inode in fuse_fill_super_submount | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
|
MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-09-17T16:06:37.179Z
Reserved: 2026-09-11T19:38:34.789Z
Link: CVE-2026-90139
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-09-17T17:17:06.523
Modified: 2026-09-17T17:17:06.523
Link: CVE-2026-90139
Redhat
No data.
OpenCVE Enrichment
No data.
Weaknesses
No weakness.