7.8
CWE
415
Advisory Published
Updated

CVE-2024-49882: ext4: fix double brelse() the buffer of the extents path

First published: Mon Oct 21 2024(Updated: )

In the Linux kernel, the following vulnerability has been resolved: ext4: fix double brelse() the buffer of the extents path In ext4_ext_try_to_merge_up(), set path[1].p_bh to NULL after it has been released, otherwise it may be released twice. An example of what triggers this is as follows: split2 map split1 |--------|-------|--------| ext4_ext_map_blocks ext4_ext_handle_unwritten_extents ext4_split_convert_extents // path->p_depth == 0 ext4_split_extent // 1. do split1 ext4_split_extent_at |ext4_ext_insert_extent | ext4_ext_create_new_leaf | ext4_ext_grow_indepth | le16_add_cpu(&neh->eh_depth, 1) | ext4_find_extent | // return -ENOMEM |// get error and try zeroout |path = ext4_find_extent | path->p_depth = 1 |ext4_ext_try_to_merge | ext4_ext_try_to_merge_up | path->p_depth = 0 | brelse(path[1].p_bh) ---> not set to NULL here |// zeroout success // 2. update path ext4_find_extent // 3. do split2 ext4_split_extent_at ext4_ext_insert_extent ext4_ext_create_new_leaf ext4_ext_grow_indepth le16_add_cpu(&neh->eh_depth, 1) ext4_find_extent path[0].p_bh = NULL; path->p_depth = 1 read_extent_tree_block ---> return err // path[1].p_bh is still the old value ext4_free_ext_path ext4_ext_drop_refs // path->p_depth == 1 brelse(path[1].p_bh) ---> brelse a buffer twice Finally got the following WARRNING when removing the buffer from lru: ============================================ VFS: brelse: Trying to free free buffer WARNING: CPU: 2 PID: 72 at fs/buffer.c:1241 __brelse+0x58/0x90 CPU: 2 PID: 72 Comm: kworker/u19:1 Not tainted 6.9.0-dirty #716 RIP: 0010:__brelse+0x58/0x90 Call Trace: <TASK> __find_get_block+0x6e7/0x810 bdev_getblk+0x2b/0x480 __ext4_get_inode_loc+0x48a/0x1240 ext4_get_inode_loc+0xb2/0x150 ext4_reserve_inode_write+0xb7/0x230 __ext4_mark_inode_dirty+0x144/0x6a0 ext4_ext_insert_extent+0x9c8/0x3230 ext4_ext_map_blocks+0xf45/0x2dc0 ext4_map_blocks+0x724/0x1700 ext4_do_writepages+0x12d6/0x2a70 [...] ============================================

Credit: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 416baaa9-dc9f-4396-8d5f-8c081fb06d67

Affected SoftwareAffected VersionHow to fix
Linux Kernel>=3.7<5.10.227
Linux Kernel>=5.11<5.15.168
Linux Kernel>=5.16<6.1.113
Linux Kernel>=6.2<6.6.55
Linux Kernel>=6.7<6.10.14
Linux Kernel>=6.11<6.11.3
debian/linux<=5.10.223-1<=5.10.226-1
6.1.123-1
6.1.128-1
6.12.12-1
6.12.15-1
debian/linux-6.1
6.1.119-1~deb11u1

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Frequently Asked Questions

  • What is the severity of CVE-2024-49882?

    CVE-2024-49882 has a moderate severity rating due to the potential for double buffer release in the ext4 file system.

  • How do I fix CVE-2024-49882?

    To fix CVE-2024-49882, update to the latest patched versions of the Linux kernel or any specific secure versions provided by your Linux distribution.

  • Which versions of the Linux kernel are affected by CVE-2024-49882?

    CVE-2024-49882 affects various Linux kernel versions from 3.7 up to 6.11.3, with multiple specific sub-versions in between.

  • What is the cause of CVE-2024-49882?

    CVE-2024-49882 is caused by a failure to set the path buffer to NULL after releasing it, leading to potential double release issues.

  • Is there a public reference for CVE-2024-49882?

    Yes, there are public references available for CVE-2024-49882 on the kernel.org stable repositories.

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