CVE-2025-68264

Summary

In the Linux kernel, the following vulnerability has been resolved:

ext4: refresh inline data size before write operations

The cached ei->i_inline_size can become stale between the initial size check and when ext4_update_inline_data()/ext4_create_inline_data() use it. Although ext4_get_max_inline_size() reads the correct value at the time of the check, concurrent xattr operations can modify i_inline_size before ext4_write_lock_xattr() is acquired.

This causes ext4_update_inline_data() and ext4_create_inline_data() to work with stale capacity values, leading to a BUG_ON() crash in ext4_write_inline_data():

kernel BUG at fs/ext4/inline.c:1331! BUG_ON(pos + len > EXT4_I(inode)->i_inline_size);

The race window:

1. ext4_get_max_inline_size() reads i_inline_size = 60 (correct)
2. Size check passes for 50-byte write
3. [Another thread adds xattr, i_inline_size changes to 40]
4. ext4_write_lock_xattr() acquires lock
5. ext4_update_inline_data() uses stale i_inline_size = 60
6. Attempts to write 50 bytes but only 40 bytes actually available
7. BUG_ON() triggers

Fix this by recalculating i_inline_size via ext4_find_inline_data_nolock() immediately after acquiring xattr_sem. This ensures ext4_update_inline_data() and ext4_create_inline_data() work with current values that are protected from concurrent modifications.

This is similar to commit a54c4613dac1 ("ext4: fix race writing to an inline_data file while its xattrs are changing") which fixed i_inline_off staleness. This patch addresses the related i_inline_size staleness issue.

Affected Software

Weaknesses

ADP Enrichment

CISA ADP Vulnrichment

• SSVC:
• Exploitation: none
  • Automatable: no
  • Technical Impact: partial

References

• https://git.kernel.org/stable/c/54ab81ae5f218452e64470cd8a8139bb5880fe2b
• https://git.kernel.org/stable/c/43bf001f0fe4e59bba47c897505222f959f4a1cc
• https://git.kernel.org/stable/c/89c2c41f0974e530b2d032c3695095aa0559adb1
• https://git.kernel.org/stable/c/1687a055a555347b002f406676a1aaae4668f242
• https://git.kernel.org/stable/c/210ac60a86a3ad2c76ae60e0dc71c34af6e7ea0b
• https://git.kernel.org/stable/c/ca43ea29b4c4d2764aec8a26cffcfb677a871e6e
• https://git.kernel.org/stable/c/58df743faf21ceb1880f930aa5dd428e2a5e415d
• https://git.kernel.org/stable/c/892e1cf17555735e9d021ab036c36bc7b58b0e3b

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