ghsa-grj2-x9v7-7qqx
Vulnerability from github
Published
2024-09-13 06:30
Modified
2024-09-16 14:37
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Details

In the Linux kernel, the following vulnerability has been resolved:

btrfs: fix a use-after-free when hitting errors inside btrfs_submit_chunk()

[BUG] There is an internal report that KASAN is reporting use-after-free, with the following backtrace:

BUG: KASAN: slab-use-after-free in btrfs_check_read_bio+0xa68/0xb70 [btrfs] Read of size 4 at addr ffff8881117cec28 by task kworker/u16:2/45 CPU: 1 UID: 0 PID: 45 Comm: kworker/u16:2 Not tainted 6.11.0-rc2-next-20240805-default+ #76 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.2-3-gd478f380-rebuilt.opensuse.org 04/01/2014 Workqueue: btrfs-endio btrfs_end_bio_work [btrfs] Call Trace: dump_stack_lvl+0x61/0x80 print_address_description.constprop.0+0x5e/0x2f0 print_report+0x118/0x216 kasan_report+0x11d/0x1f0 btrfs_check_read_bio+0xa68/0xb70 [btrfs] process_one_work+0xce0/0x12a0 worker_thread+0x717/0x1250 kthread+0x2e3/0x3c0 ret_from_fork+0x2d/0x70 ret_from_fork_asm+0x11/0x20

Allocated by task 20917: kasan_save_stack+0x37/0x60 kasan_save_track+0x10/0x30 __kasan_slab_alloc+0x7d/0x80 kmem_cache_alloc_noprof+0x16e/0x3e0 mempool_alloc_noprof+0x12e/0x310 bio_alloc_bioset+0x3f0/0x7a0 btrfs_bio_alloc+0x2e/0x50 [btrfs] submit_extent_page+0x4d1/0xdb0 [btrfs] btrfs_do_readpage+0x8b4/0x12a0 [btrfs] btrfs_readahead+0x29a/0x430 [btrfs] read_pages+0x1a7/0xc60 page_cache_ra_unbounded+0x2ad/0x560 filemap_get_pages+0x629/0xa20 filemap_read+0x335/0xbf0 vfs_read+0x790/0xcb0 ksys_read+0xfd/0x1d0 do_syscall_64+0x6d/0x140 entry_SYSCALL_64_after_hwframe+0x4b/0x53

Freed by task 20917: kasan_save_stack+0x37/0x60 kasan_save_track+0x10/0x30 kasan_save_free_info+0x37/0x50 __kasan_slab_free+0x4b/0x60 kmem_cache_free+0x214/0x5d0 bio_free+0xed/0x180 end_bbio_data_read+0x1cc/0x580 [btrfs] btrfs_submit_chunk+0x98d/0x1880 [btrfs] btrfs_submit_bio+0x33/0x70 [btrfs] submit_one_bio+0xd4/0x130 [btrfs] submit_extent_page+0x3ea/0xdb0 [btrfs] btrfs_do_readpage+0x8b4/0x12a0 [btrfs] btrfs_readahead+0x29a/0x430 [btrfs] read_pages+0x1a7/0xc60 page_cache_ra_unbounded+0x2ad/0x560 filemap_get_pages+0x629/0xa20 filemap_read+0x335/0xbf0 vfs_read+0x790/0xcb0 ksys_read+0xfd/0x1d0 do_syscall_64+0x6d/0x140 entry_SYSCALL_64_after_hwframe+0x4b/0x53

[CAUSE] Although I cannot reproduce the error, the report itself is good enough to pin down the cause.

The call trace is the regular endio workqueue context, but the free-by-task trace is showing that during btrfs_submit_chunk() we already hit a critical error, and is calling btrfs_bio_end_io() to error out. And the original endio function called bio_put() to free the whole bio.

This means a double freeing thus causing use-after-free, e.g.:

  1. Enter btrfs_submit_bio() with a read bio The read bio length is 128K, crossing two 64K stripes.

  2. The first run of btrfs_submit_chunk()

2.1 Call btrfs_map_block(), which returns 64K 2.2 Call btrfs_split_bio() Now there are two bios, one referring to the first 64K, the other referring to the second 64K. 2.3 The first half is submitted.

  1. The second run of btrfs_submit_chunk()

3.1 Call btrfs_map_block(), which by somehow failed Now we call btrfs_bio_end_io() to handle the error

3.2 btrfs_bio_end_io() calls the original endio function Which is end_bbio_data_read(), and it calls bio_put() for the original bio.

Now the original bio is freed.
  1. The submitted first 64K bio finished Now we call into btrfs_check_read_bio() and tries to advance the bio iter. But since the original bio (thus its iter) is already freed, we trigger the above use-after free.

And even if the memory is not poisoned/corrupted, we will later call the original endio function, causing a double freeing.

[FIX] Instead of calling btrfs_bio_end_io(), call btrfs_orig_bbio_end_io(), which has the extra check on split bios and do the pr ---truncated---

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{
  "affected": [],
  "aliases": [
    "CVE-2024-46687"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-415"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2024-09-13T06:15:13Z",
    "severity": "HIGH"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: fix a use-after-free when hitting errors inside btrfs_submit_chunk()\n\n[BUG]\nThere is an internal report that KASAN is reporting use-after-free, with\nthe following backtrace:\n\n  BUG: KASAN: slab-use-after-free in btrfs_check_read_bio+0xa68/0xb70 [btrfs]\n  Read of size 4 at addr ffff8881117cec28 by task kworker/u16:2/45\n  CPU: 1 UID: 0 PID: 45 Comm: kworker/u16:2 Not tainted 6.11.0-rc2-next-20240805-default+ #76\n  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.2-3-gd478f380-rebuilt.opensuse.org 04/01/2014\n  Workqueue: btrfs-endio btrfs_end_bio_work [btrfs]\n  Call Trace:\n   dump_stack_lvl+0x61/0x80\n   print_address_description.constprop.0+0x5e/0x2f0\n   print_report+0x118/0x216\n   kasan_report+0x11d/0x1f0\n   btrfs_check_read_bio+0xa68/0xb70 [btrfs]\n   process_one_work+0xce0/0x12a0\n   worker_thread+0x717/0x1250\n   kthread+0x2e3/0x3c0\n   ret_from_fork+0x2d/0x70\n   ret_from_fork_asm+0x11/0x20\n\n  Allocated by task 20917:\n   kasan_save_stack+0x37/0x60\n   kasan_save_track+0x10/0x30\n   __kasan_slab_alloc+0x7d/0x80\n   kmem_cache_alloc_noprof+0x16e/0x3e0\n   mempool_alloc_noprof+0x12e/0x310\n   bio_alloc_bioset+0x3f0/0x7a0\n   btrfs_bio_alloc+0x2e/0x50 [btrfs]\n   submit_extent_page+0x4d1/0xdb0 [btrfs]\n   btrfs_do_readpage+0x8b4/0x12a0 [btrfs]\n   btrfs_readahead+0x29a/0x430 [btrfs]\n   read_pages+0x1a7/0xc60\n   page_cache_ra_unbounded+0x2ad/0x560\n   filemap_get_pages+0x629/0xa20\n   filemap_read+0x335/0xbf0\n   vfs_read+0x790/0xcb0\n   ksys_read+0xfd/0x1d0\n   do_syscall_64+0x6d/0x140\n   entry_SYSCALL_64_after_hwframe+0x4b/0x53\n\n  Freed by task 20917:\n   kasan_save_stack+0x37/0x60\n   kasan_save_track+0x10/0x30\n   kasan_save_free_info+0x37/0x50\n   __kasan_slab_free+0x4b/0x60\n   kmem_cache_free+0x214/0x5d0\n   bio_free+0xed/0x180\n   end_bbio_data_read+0x1cc/0x580 [btrfs]\n   btrfs_submit_chunk+0x98d/0x1880 [btrfs]\n   btrfs_submit_bio+0x33/0x70 [btrfs]\n   submit_one_bio+0xd4/0x130 [btrfs]\n   submit_extent_page+0x3ea/0xdb0 [btrfs]\n   btrfs_do_readpage+0x8b4/0x12a0 [btrfs]\n   btrfs_readahead+0x29a/0x430 [btrfs]\n   read_pages+0x1a7/0xc60\n   page_cache_ra_unbounded+0x2ad/0x560\n   filemap_get_pages+0x629/0xa20\n   filemap_read+0x335/0xbf0\n   vfs_read+0x790/0xcb0\n   ksys_read+0xfd/0x1d0\n   do_syscall_64+0x6d/0x140\n   entry_SYSCALL_64_after_hwframe+0x4b/0x53\n\n[CAUSE]\nAlthough I cannot reproduce the error, the report itself is good enough\nto pin down the cause.\n\nThe call trace is the regular endio workqueue context, but the\nfree-by-task trace is showing that during btrfs_submit_chunk() we\nalready hit a critical error, and is calling btrfs_bio_end_io() to error\nout.  And the original endio function called bio_put() to free the whole\nbio.\n\nThis means a double freeing thus causing use-after-free, e.g.:\n\n1. Enter btrfs_submit_bio() with a read bio\n   The read bio length is 128K, crossing two 64K stripes.\n\n2. The first run of btrfs_submit_chunk()\n\n2.1 Call btrfs_map_block(), which returns 64K\n2.2 Call btrfs_split_bio()\n    Now there are two bios, one referring to the first 64K, the other\n    referring to the second 64K.\n2.3 The first half is submitted.\n\n3. The second run of btrfs_submit_chunk()\n\n3.1 Call btrfs_map_block(), which by somehow failed\n    Now we call btrfs_bio_end_io() to handle the error\n\n3.2 btrfs_bio_end_io() calls the original endio function\n    Which is end_bbio_data_read(), and it calls bio_put() for the\n    original bio.\n\n    Now the original bio is freed.\n\n4. The submitted first 64K bio finished\n   Now we call into btrfs_check_read_bio() and tries to advance the bio\n   iter.\n   But since the original bio (thus its iter) is already freed, we\n   trigger the above use-after free.\n\n   And even if the memory is not poisoned/corrupted, we will later call\n   the original endio function, causing a double freeing.\n\n[FIX]\nInstead of calling btrfs_bio_end_io(), call btrfs_orig_bbio_end_io(),\nwhich has the extra check on split bios and do the pr\n---truncated---",
  "id": "GHSA-grj2-x9v7-7qqx",
  "modified": "2024-09-16T14:37:26Z",
  "published": "2024-09-13T06:30:43Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2024-46687"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/10d9d8c3512f16cad47b2ff81ec6fc4b27d8ee10"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/4a3b9e1a8e6cd1a8d427a905e159de58d38941cc"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/51722b99f41f5e722ffa10b8f61e802a0e70b331"
    }
  ],
  "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"
    }
  ]
}


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