ghsa-2gwr-frhx-j93x
Vulnerability from github
In the Linux kernel, the following vulnerability has been resolved:
ubifs: authentication: Fix use-after-free in ubifs_tnc_end_commit
After an insertion in TNC, the tree might split and cause a node to
change its znode->parent
. A further deletion of other nodes in the
tree (which also could free the nodes), the aforementioned node's
znode->cparent
could still point to a freed node. This
znode->cparent
may not be updated when getting nodes to commit in
ubifs_tnc_start_commit()
. This could then trigger a use-after-free
when accessing the znode->cparent
in write_index()
in
ubifs_tnc_end_commit()
.
This can be triggered by running
rm -f /etc/test-file.bin dd if=/dev/urandom of=/etc/test-file.bin bs=1M count=60 conv=fsync
in a loop, and with CONFIG_UBIFS_FS_AUTHENTICATION
. KASAN then
reports:
BUG: KASAN: use-after-free in ubifs_tnc_end_commit+0xa5c/0x1950 Write of size 32 at addr ffffff800a3af86c by task ubifs_bgt0_20/153
Call trace: dump_backtrace+0x0/0x340 show_stack+0x18/0x24 dump_stack_lvl+0x9c/0xbc print_address_description.constprop.0+0x74/0x2b0 kasan_report+0x1d8/0x1f0 kasan_check_range+0xf8/0x1a0 memcpy+0x84/0xf4 ubifs_tnc_end_commit+0xa5c/0x1950 do_commit+0x4e0/0x1340 ubifs_bg_thread+0x234/0x2e0 kthread+0x36c/0x410 ret_from_fork+0x10/0x20
Allocated by task 401: kasan_save_stack+0x38/0x70 __kasan_kmalloc+0x8c/0xd0 __kmalloc+0x34c/0x5bc tnc_insert+0x140/0x16a4 ubifs_tnc_add+0x370/0x52c ubifs_jnl_write_data+0x5d8/0x870 do_writepage+0x36c/0x510 ubifs_writepage+0x190/0x4dc __writepage+0x58/0x154 write_cache_pages+0x394/0x830 do_writepages+0x1f0/0x5b0 filemap_fdatawrite_wbc+0x170/0x25c file_write_and_wait_range+0x140/0x190 ubifs_fsync+0xe8/0x290 vfs_fsync_range+0xc0/0x1e4 do_fsync+0x40/0x90 __arm64_sys_fsync+0x34/0x50 invoke_syscall.constprop.0+0xa8/0x260 do_el0_svc+0xc8/0x1f0 el0_svc+0x34/0x70 el0t_64_sync_handler+0x108/0x114 el0t_64_sync+0x1a4/0x1a8
Freed by task 403: kasan_save_stack+0x38/0x70 kasan_set_track+0x28/0x40 kasan_set_free_info+0x28/0x4c __kasan_slab_free+0xd4/0x13c kfree+0xc4/0x3a0 tnc_delete+0x3f4/0xe40 ubifs_tnc_remove_range+0x368/0x73c ubifs_tnc_remove_ino+0x29c/0x2e0 ubifs_jnl_delete_inode+0x150/0x260 ubifs_evict_inode+0x1d4/0x2e4 evict+0x1c8/0x450 iput+0x2a0/0x3c4 do_unlinkat+0x2cc/0x490 __arm64_sys_unlinkat+0x90/0x100 invoke_syscall.constprop.0+0xa8/0x260 do_el0_svc+0xc8/0x1f0 el0_svc+0x34/0x70 el0t_64_sync_handler+0x108/0x114 el0t_64_sync+0x1a4/0x1a8
The offending memcpy()
in ubifs_copy_hash()
has a use-after-free
when a node becomes root in TNC but still has a cparent
to an already
freed node. More specifically, consider the following TNC:
zroot
/
/
zp1
/
/
zn
Inserting a new node zn_new
with a key smaller then zn
will trigger
a split in tnc_insert()
if zp1
is full:
zroot
/ \
/ \
zp1 zp2
/ \
/ \
zn_new zn
zn->parent
has now been moved to zp2
, but zn->cparent
still
points to zp1
.
Now, consider a removal of all the nodes except zn
. Just when
tnc_delete()
is about to delete zroot
and zp2
:
zroot
\
\
zp2
\
\
zn
zroot
and zp2
get freed and the tree collapses:
zn
zn
now becomes the new zroot
.
get_znodes_to_commit()
will now only find zn
, the new zroot
, and
write_index()
will check its znode->cparent
that wrongly points to
the already freed zp1
. ubifs_copy_hash()
thus gets wrongly called
with znode->cparent->zbranch[znode->iip].hash
that triggers the
use-after-free!
Fix this by explicitly setting znode->cparent
to NULL
in
get_znodes_to_commit()
for the root node. The search for the dirty
nodes
---truncated---
{ "affected": [], "aliases": [ "CVE-2024-53171" ], "database_specific": { "cwe_ids": [ "CWE-416" ], "github_reviewed": false, "github_reviewed_at": null, "nvd_published_at": "2024-12-27T14:15:24Z", "severity": "HIGH" }, "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nubifs: authentication: Fix use-after-free in ubifs_tnc_end_commit\n\nAfter an insertion in TNC, the tree might split and cause a node to\nchange its `znode-\u003eparent`. A further deletion of other nodes in the\ntree (which also could free the nodes), the aforementioned node\u0027s\n`znode-\u003ecparent` could still point to a freed node. This\n`znode-\u003ecparent` may not be updated when getting nodes to commit in\n`ubifs_tnc_start_commit()`. This could then trigger a use-after-free\nwhen accessing the `znode-\u003ecparent` in `write_index()` in\n`ubifs_tnc_end_commit()`.\n\nThis can be triggered by running\n\n rm -f /etc/test-file.bin\n dd if=/dev/urandom of=/etc/test-file.bin bs=1M count=60 conv=fsync\n\nin a loop, and with `CONFIG_UBIFS_FS_AUTHENTICATION`. KASAN then\nreports:\n\n BUG: KASAN: use-after-free in ubifs_tnc_end_commit+0xa5c/0x1950\n Write of size 32 at addr ffffff800a3af86c by task ubifs_bgt0_20/153\n\n Call trace:\n dump_backtrace+0x0/0x340\n show_stack+0x18/0x24\n dump_stack_lvl+0x9c/0xbc\n print_address_description.constprop.0+0x74/0x2b0\n kasan_report+0x1d8/0x1f0\n kasan_check_range+0xf8/0x1a0\n memcpy+0x84/0xf4\n ubifs_tnc_end_commit+0xa5c/0x1950\n do_commit+0x4e0/0x1340\n ubifs_bg_thread+0x234/0x2e0\n kthread+0x36c/0x410\n ret_from_fork+0x10/0x20\n\n Allocated by task 401:\n kasan_save_stack+0x38/0x70\n __kasan_kmalloc+0x8c/0xd0\n __kmalloc+0x34c/0x5bc\n tnc_insert+0x140/0x16a4\n ubifs_tnc_add+0x370/0x52c\n ubifs_jnl_write_data+0x5d8/0x870\n do_writepage+0x36c/0x510\n ubifs_writepage+0x190/0x4dc\n __writepage+0x58/0x154\n write_cache_pages+0x394/0x830\n do_writepages+0x1f0/0x5b0\n filemap_fdatawrite_wbc+0x170/0x25c\n file_write_and_wait_range+0x140/0x190\n ubifs_fsync+0xe8/0x290\n vfs_fsync_range+0xc0/0x1e4\n do_fsync+0x40/0x90\n __arm64_sys_fsync+0x34/0x50\n invoke_syscall.constprop.0+0xa8/0x260\n do_el0_svc+0xc8/0x1f0\n el0_svc+0x34/0x70\n el0t_64_sync_handler+0x108/0x114\n el0t_64_sync+0x1a4/0x1a8\n\n Freed by task 403:\n kasan_save_stack+0x38/0x70\n kasan_set_track+0x28/0x40\n kasan_set_free_info+0x28/0x4c\n __kasan_slab_free+0xd4/0x13c\n kfree+0xc4/0x3a0\n tnc_delete+0x3f4/0xe40\n ubifs_tnc_remove_range+0x368/0x73c\n ubifs_tnc_remove_ino+0x29c/0x2e0\n ubifs_jnl_delete_inode+0x150/0x260\n ubifs_evict_inode+0x1d4/0x2e4\n evict+0x1c8/0x450\n iput+0x2a0/0x3c4\n do_unlinkat+0x2cc/0x490\n __arm64_sys_unlinkat+0x90/0x100\n invoke_syscall.constprop.0+0xa8/0x260\n do_el0_svc+0xc8/0x1f0\n el0_svc+0x34/0x70\n el0t_64_sync_handler+0x108/0x114\n el0t_64_sync+0x1a4/0x1a8\n\nThe offending `memcpy()` in `ubifs_copy_hash()` has a use-after-free\nwhen a node becomes root in TNC but still has a `cparent` to an already\nfreed node. More specifically, consider the following TNC:\n\n zroot\n /\n /\n zp1\n /\n /\n zn\n\nInserting a new node `zn_new` with a key smaller then `zn` will trigger\na split in `tnc_insert()` if `zp1` is full:\n\n zroot\n / \\\n / \\\n zp1 zp2\n / \\\n / \\\n zn_new zn\n\n`zn-\u003eparent` has now been moved to `zp2`, *but* `zn-\u003ecparent` still\npoints to `zp1`.\n\nNow, consider a removal of all the nodes _except_ `zn`. Just when\n`tnc_delete()` is about to delete `zroot` and `zp2`:\n\n zroot\n \\\n \\\n zp2\n \\\n \\\n zn\n\n`zroot` and `zp2` get freed and the tree collapses:\n\n zn\n\n`zn` now becomes the new `zroot`.\n\n`get_znodes_to_commit()` will now only find `zn`, the new `zroot`, and\n`write_index()` will check its `znode-\u003ecparent` that wrongly points to\nthe already freed `zp1`. `ubifs_copy_hash()` thus gets wrongly called\nwith `znode-\u003ecparent-\u003ezbranch[znode-\u003eiip].hash` that triggers the\nuse-after-free!\n\nFix this by explicitly setting `znode-\u003ecparent` to `NULL` in\n`get_znodes_to_commit()` for the root node. The search for the dirty\nnodes\n---truncated---", "id": "GHSA-2gwr-frhx-j93x", "modified": "2025-01-14T18:31:53Z", "published": "2024-12-27T15:31:50Z", "references": [ { "type": "ADVISORY", "url": "https://nvd.nist.gov/vuln/detail/CVE-2024-53171" }, { "type": "WEB", "url": "https://git.kernel.org/stable/c/01d3a2293d7e4edfff96618c15727db7e51f11b6" }, { "type": "WEB", "url": "https://git.kernel.org/stable/c/2497479aecebe869d23a0064e0fd1a03e34f0e2a" }, { "type": "WEB", "url": "https://git.kernel.org/stable/c/398a91599d263e41c5f95a2fd4ebdb6280b5c6c3" }, { "type": "WEB", "url": "https://git.kernel.org/stable/c/4617fb8fc15effe8eda4dd898d4e33eb537a7140" }, { "type": "WEB", "url": "https://git.kernel.org/stable/c/4d9807048b851d7a58d5bd089c16254af896e4df" }, { "type": "WEB", "url": "https://git.kernel.org/stable/c/74981f7577d183acad1cd58f74c10d263711a215" }, { "type": "WEB", "url": "https://git.kernel.org/stable/c/8d8b3f5f4cbfbf6cb0ea4a4d5dc296872b4151eb" }, { "type": "WEB", "url": "https://git.kernel.org/stable/c/daac4aa1825de0dbc1a6eede2fa7f9fc53f14223" } ], "schema_version": "1.4.0", "severity": [ { "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "type": "CVSS_V3" } ] }
Sightings
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Nomenclature
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