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Double Free Affecting kernel-coco package, versions <6.4.0-15061.6.coco15sp6.1

Severity

 Recommended
0.0
medium
0
10

Based on SUSE Linux Enterprise Server security rating.

Threat Intelligence

EPSS
0.04% (6th percentile)

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  • Snyk IDSNYK-SLES156-KERNELCOCO-8170722
  • published9 Oct 2024
  • disclosed8 Oct 2024
Report a new vulnerability Found a mistake?

Introduced: 8 Oct 2024

CVE-2024-46687  (opens in a new tab)
CWE-415  (opens in a new tab)
CWE-416  (opens in a new tab)

How to fix?

Upgrade SLES:15.6 kernel-coco to version 6.4.0-15061.6.coco15sp6.1 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-coco package and not the kernel-coco package as distributed by SLES. See How to fix? for SLES:15.6 relevant fixed versions and status.

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---

CVSS Scores

version 3.1