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Message-ID: <2025120935-CVE-2022-50638-fb89@gregkh> Date: Tue, 9 Dec 2025 09:01:39 +0900 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-cve-announce@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...nel.org> Subject: CVE-2022-50638: ext4: fix bug_on in __es_tree_search caused by bad boot loader inode From: Greg Kroah-Hartman <gregkh@...nel.org> 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: <TASK> __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 </TASK> ================================================================== 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. The Linux kernel CVE team has assigned CVE-2022-50638 to this issue. Affected and fixed versions =========================== Fixed in 4.9.337 with commit e76ede9d2c9e0af4573342b56d7cdbf757c18084 Fixed in 4.14.303 with commit a95ba369255ddcdc5e43d38bc5203537bdf3a518 Fixed in 4.19.270 with commit 5f8d36abd2059bf1bd016b17d1fe78d8613deddd Fixed in 5.4.229 with commit 78e335fb573e6a85718c4c24d5a052718a99a9ed Fixed in 5.10.163 with commit 71e99ec1315fe98d322b17b9a28f204aaf15ffee Fixed in 5.15.87 with commit d480a49c15c465cb9a16db1379f4996e9b5bb9cc Fixed in 6.0.18 with commit feec0ea94c5ef4aa118750284c8a921698733ef2 Fixed in 6.1.4 with commit a125c8806b7d3c3815b6f9f59d395b9d7527b0ef Fixed in 6.2 with commit 991ed014de0840c5dc405b679168924afb2952ac Please see https://www.kernel.org for a full list of currently supported kernel versions by the kernel community. Unaffected versions might change over time as fixes are backported to older supported kernel versions. The official CVE entry at https://cve.org/CVERecord/?id=CVE-2022-50638 will be updated if fixes are backported, please check that for the most up to date information about this issue. Affected files ============== The file(s) affected by this issue are: fs/ext4/ioctl.c Mitigation ========== The Linux kernel CVE team recommends that you update to the latest stable kernel version for this, and many other bugfixes. Individual changes are never tested alone, but rather are part of a larger kernel release. Cherry-picking individual commits is not recommended or supported by the Linux kernel community at all. If however, updating to the latest release is impossible, the individual changes to resolve this issue can be found at these commits: https://git.kernel.org/stable/c/e76ede9d2c9e0af4573342b56d7cdbf757c18084 https://git.kernel.org/stable/c/a95ba369255ddcdc5e43d38bc5203537bdf3a518 https://git.kernel.org/stable/c/5f8d36abd2059bf1bd016b17d1fe78d8613deddd https://git.kernel.org/stable/c/78e335fb573e6a85718c4c24d5a052718a99a9ed https://git.kernel.org/stable/c/71e99ec1315fe98d322b17b9a28f204aaf15ffee https://git.kernel.org/stable/c/d480a49c15c465cb9a16db1379f4996e9b5bb9cc https://git.kernel.org/stable/c/feec0ea94c5ef4aa118750284c8a921698733ef2 https://git.kernel.org/stable/c/a125c8806b7d3c3815b6f9f59d395b9d7527b0ef https://git.kernel.org/stable/c/991ed014de0840c5dc405b679168924afb2952ac
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