CVE-2022-50638
Description
In the Linux kernel, the following vulnerability has been resolved:
ext4: fix bug_on in __es_tree_search caused by bad boot loader inode
We got a issue as fllows: ================================================================== kernel BUG at fs/ext4/extents_status.c:203! invalid opcode: 0000 [#1] PREEMPT SMP CPU: 1 PID: 945 Comm: cat Not tainted 6.0.0-next-20221007-dirty #349 RIP: 0010:ext4_es_end.isra.0+0x34/0x42 RSP: 0018:ffffc9000143b768 EFLAGS: 00010203 RAX: 0000000000000000 RBX: ffff8881769cd0b8 RCX: 0000000000000000 RDX: 0000000000000000 RSI: ffffffff8fc27cf7 RDI: 00000000ffffffff RBP: ffff8881769cd0bc R08: 0000000000000000 R09: ffffc9000143b5f8 R10: 0000000000000001 R11: 0000000000000001 R12: ffff8881769cd0a0 R13: ffff8881768e5668 R14: 00000000768e52f0 R15: 0000000000000000 FS: 00007f359f7f05c0(0000)GS:ffff88842fd00000(0000)knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f359f5a2000 CR3: 000000017130c000 CR4: 00000000000006e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace:
__es_tree_search.isra.0+0x6d/0xf5 ext4_es_cache_extent+0xfa/0x230 ext4_cache_extents+0xd2/0x110 ext4_find_extent+0x5d5/0x8c0 ext4_ext_map_blocks+0x9c/0x1d30 ext4_map_blocks+0x431/0xa50 ext4_mpage_readpages+0x48e/0xe40 ext4_readahead+0x47/0x50 read_pages+0x82/0x530 page_cache_ra_unbounded+0x199/0x2a0 do_page_cache_ra+0x47/0x70 page_cache_ra_order+0x242/0x400 ondemand_readahead+0x1e8/0x4b0 page_cache_sync_ra+0xf4/0x110 filemap_get_pages+0x131/0xb20 filemap_read+0xda/0x4b0 generic_file_read_iter+0x13a/0x250 ext4_file_read_iter+0x59/0x1d0 vfs_read+0x28f/0x460 ksys_read+0x73/0x160 __x64_sys_read+0x1e/0x30 do_syscall_64+0x35/0x80 entry_SYSCALL_64_after_hwframe+0x63/0xcd
==================================================================
In the above issue, ioctl invokes the swap_inode_boot_loader function to swap inode<5> and inode<12>. However, inode<5> contain incorrect imode and disordered extents, and i_nlink is set to 1. The extents check for inode in the ext4_iget function can be bypassed bacause 5 is EXT4_BOOT_LOADER_INO. While links_count is set to 1, the extents are not initialized in swap_inode_boot_loader. After the ioctl command is executed successfully, the extents are swapped to inode<12>, in this case, run the cat command to view inode<12>. And Bug_ON is triggered due to the incorrect extents.
When the boot loader inode is not initialized, its imode can be one of the following: 1) the imode is a bad type, which is marked as bad_inode in ext4_iget and set to S_IFREG. 2) the imode is good type but not S_IFREG. 3) the imode is S_IFREG.
The BUG_ON may be triggered by bypassing the check in cases 1 and 2. Therefore, when the boot loader inode is bad_inode or its imode is not S_IFREG, initialize the inode to avoid triggering the BUG.
AI Insight
LLM-synthesized narrative grounded in this CVE's description and references.
A local attacker can trigger a kernel panic in the Linux kernel's ext4 filesystem by exploiting a bad boot loader inode swap, causing a BUG_ON in the extent status tree search.
Vulnerability
Description
CVE-2022-50638 is a denial-of-service vulnerability in the Linux kernel's ext4 filesystem. The root cause is that the swap_inode_boot_loader function, invoked via an ioctl, can exchange a regular inode (e.g., inode 5) with a boot loader inode that has a corrupted extent tree. This results in a kernel BUG_ON in __es_tree_search at fs/ext4/extents_status.c:203 when the filesystem tries to cache extent status for the swapped-in inode.
Exploitation
An attacker must have local access to the system and the ability to call the EXT4_IOC_SWAP_BOOT ioctl, which typically requires privileges such as CAP_SYS_ADMIN or root. No authentication is needed beyond local shell access with the appropriate capability. The attacker crafts a filesystem state with a malformed boot loader inode to trigger the panic during a read operation.
Impact
The vulnerability causes a kernel BUG, leading to a system crash (kernel panic) and thus a denial of service. The panic message shows an invalid opcode in ext4_es_end, indicating illegal access to the extent status tree. No privilege escalation or data integrity loss is described in the available reports.
Mitigation
The issue is fixed in Linux kernel stable updates containing commits [1], [2], [3], and [4], which were backported to various stable series. Users should update their kernels to incorporate these patches. No workaround is available other than limiting access to the vulnerable ioctl or removing the swap_inode_boot_loader functionality if not required.
AI Insight generated on May 19, 2026. Synthesized from this CVE's description and the cited reference URLs; citations are validated against the source bundle.
Affected products
3Patches
9e76ede9d2c9ea95ba369255d5f8d36abd20578e335fb573e71e99ec1315fd480a49c15c4feec0ea94c5ea125c8806b7d991ed014de08Vulnerability mechanics
Generated on May 9, 2026. Inputs: CWE entries + fix-commit diffs from this CVE's patches. Citations validated against bundle.
References
9- git.kernel.org/stable/c/5f8d36abd2059bf1bd016b17d1fe78d8613dedddnvd
- git.kernel.org/stable/c/71e99ec1315fe98d322b17b9a28f204aaf15ffeenvd
- git.kernel.org/stable/c/78e335fb573e6a85718c4c24d5a052718a99a9ednvd
- git.kernel.org/stable/c/991ed014de0840c5dc405b679168924afb2952acnvd
- git.kernel.org/stable/c/a125c8806b7d3c3815b6f9f59d395b9d7527b0efnvd
- git.kernel.org/stable/c/a95ba369255ddcdc5e43d38bc5203537bdf3a518nvd
- git.kernel.org/stable/c/d480a49c15c465cb9a16db1379f4996e9b5bb9ccnvd
- git.kernel.org/stable/c/e76ede9d2c9e0af4573342b56d7cdbf757c18084nvd
- git.kernel.org/stable/c/feec0ea94c5ef4aa118750284c8a921698733ef2nvd
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