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.
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 |
|
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Advisories
No advisories yet.
Fixes
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
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 |
|
|
Projects
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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
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OpenCVE Enrichment
No data.
Weaknesses
No weakness.