CVE-2025-68261
Description
In the Linux kernel, the following vulnerability has been resolved:
ext4: add i_data_sem protection in ext4_destroy_inline_data_nolock()
Fix a race between inline data destruction and block mapping.
The function ext4_destroy_inline_data_nolock() changes the inode data layout by clearing EXT4_INODE_INLINE_DATA and setting EXT4_INODE_EXTENTS. At the same time, another thread may execute ext4_map_blocks(), which tests EXT4_INODE_EXTENTS to decide whether to call ext4_ext_map_blocks() or ext4_ind_map_blocks().
Without i_data_sem protection, ext4_ind_map_blocks() may receive inode with EXT4_INODE_EXTENTS flag and triggering assert.
kernel BUG at fs/ext4/indirect.c:546! EXT4-fs (loop2): unmounting filesystem. invalid opcode: 0000 [#1] PREEMPT SMP KASAN NOPTI Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014 RIP: 0010:ext4_ind_map_blocks.cold+0x2b/0x5a fs/ext4/indirect.c:546
Call Trace:
ext4_map_blocks+0xb9b/0x16f0 fs/ext4/inode.c:681 _ext4_get_block+0x242/0x590 fs/ext4/inode.c:822 ext4_block_write_begin+0x48b/0x12c0 fs/ext4/inode.c:1124 ext4_write_begin+0x598/0xef0 fs/ext4/inode.c:1255 ext4_da_write_begin+0x21e/0x9c0 fs/ext4/inode.c:3000 generic_perform_write+0x259/0x5d0 mm/filemap.c:3846 ext4_buffered_write_iter+0x15b/0x470 fs/ext4/file.c:285 ext4_file_write_iter+0x8e0/0x17f0 fs/ext4/file.c:679 call_write_iter include/linux/fs.h:2271 [inline] do_iter_readv_writev+0x212/0x3c0 fs/read_write.c:735 do_iter_write+0x186/0x710 fs/read_write.c:861 vfs_iter_write+0x70/0xa0 fs/read_write.c:902 iter_file_splice_write+0x73b/0xc90 fs/splice.c:685 do_splice_from fs/splice.c:763 [inline] direct_splice_actor+0x10f/0x170 fs/splice.c:950 splice_direct_to_actor+0x33a/0xa10 fs/splice.c:896 do_splice_direct+0x1a9/0x280 fs/splice.c:1002 do_sendfile+0xb13/0x12c0 fs/read_write.c:1255 __do_sys_sendfile64 fs/read_write.c:1323 [inline] __se_sys_sendfile64 fs/read_write.c:1309 [inline] __x64_sys_sendfile64+0x1cf/0x210 fs/read_write.c:1309 do_syscall_x64 arch/x86/entry/common.c:51 [inline] do_syscall_64+0x35/0x80 arch/x86/entry/common.c:81 entry_SYSCALL_64_after_hwframe+0x6e/0xd8
AI Insight
LLM-synthesized narrative grounded in this CVE's description and references.
Race condition in ext4's inline data destruction can cause kernel BUG due to missing i_data_sem protection.
The vulnerability is a race condition in the Linux kernel's ext4 filesystem. The function ext4_destroy_inline_data_nolock() modifies the inode's data layout by clearing the EXT4_INODE_INLINE_DATA flag and setting EXT4_INODE_EXTENTS without holding the i_data_sem lock. This can race with ext4_map_blocks(), which checks the EXT4_INODE_EXTENTS flag to decide whether to use ext4_ext_map_blocks() or ext4_ind_map_blocks().
Exploitation requires local access to the filesystem and the ability to trigger concurrent operations. An attacker could cause a thread to perform inline data destruction while another thread attempts to map blocks, leading to a state where ext4_ind_map_blocks() receives an inode with the EXT4_INODE_EXTENTS flag set, triggering a kernel BUG at fs/ext4/indirect.c:546.
The impact is a denial of service (system crash) due to the kernel BUG. The vulnerability does not appear to allow privilege escalation or data corruption beyond the crash, but it can be triggered by unprivileged users with write access to an ext4 filesystem.
The issue has been fixed by adding i_data_sem protection in ext4_destroy_inline_data_nolock(). Patches have been applied to the stable kernel trees [1][2][3]. Users should update to the latest kernel versions to mitigate the vulnerability.
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
1Patches
0No patches discovered yet.
Vulnerability mechanics
AI mechanics synthesis has not run for this CVE yet.
References
8- git.kernel.org/stable/c/0cd8feea8777f8d9b9a862b89c688b049a5c8475nvd
- git.kernel.org/stable/c/144c48da33a01d92995aeccd8208eb47d2a8e659nvd
- git.kernel.org/stable/c/22a76b0861ae61a299c8e126c1aca8c4fda820fdnvd
- git.kernel.org/stable/c/5b266cf6851ce72b11b067fe02adf5a8687104adnvd
- git.kernel.org/stable/c/5cad18e527ba8a9ca5463cc170073eeb5a4826f4nvd
- git.kernel.org/stable/c/61e03dc3794ebf77a706b85e5a36c9c6d70be6denvd
- git.kernel.org/stable/c/b322bac9f01d03190b5abc52be5d9dd9f22a2b41nvd
- git.kernel.org/stable/c/ba8aeff294ac7ff6dfe293663d815c54c5ee218cnvd
News mentions
0No linked articles in our index yet.