ghsa-2gwr-frhx-j93x
Vulnerability from github
Published
2024-12-27 15:31
Modified
2025-01-14 18:31
Details

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---

Show details on source website


{
  "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"
    }
  ]
}


Log in or create an account to share your comment.




Tags
Taxonomy of the tags.


Loading…

Loading…

Loading…

Sightings

Author Source Type Date

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
  • Confirmed: The vulnerability is confirmed from an analyst perspective.
  • Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
  • Patched: This vulnerability was successfully patched by the user reporting the sighting.
  • Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
  • Not confirmed: The user expresses doubt about the veracity of the vulnerability.
  • Not patched: This vulnerability was not successfully patched by the user reporting the sighting.


Loading…

Loading…