Bug 2516927 (CVE-2026-74308)

Summary: CVE-2026-74308 kernel: ext4: fix kernel BUG in ext4_write_inline_data_end
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's ext4 filesystem. When the `data=journal` mount option is enabled, the `ext4_journalled_write_end()` function can incorrectly attempt to write inline data. This occurs if a prior attempt to convert inline data to an extent failed, leading to an inconsistent state. An attacker with local access could exploit this to trigger a kernel bug, resulting in a system crash and a Denial of Service (DoS).
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Description OSIDB Bzimport 2026-08-15 06:40:48 UTC 
In the Linux kernel, the following vulnerability has been resolved:

ext4: fix kernel BUG in ext4_write_inline_data_end

When the data=journal mount option is used, the ext4_journalled_write_end()
function incorrectly calls ext4_write_inline_data_end() without checking
if the EXT4_STATE_MAY_INLINE_DATA flag is still set on the inode.

If a previous attempt to convert the inline data to an extent failed (e.g.
due to ENOSPC), the EXT4_STATE_MAY_INLINE_DATA flag is cleared, but
the EXT4_INODE_INLINE_DATA flag remains set. In this scenario, the next
call to ext4_write_begin() will not prepare the inline data xattr for
writing, but ext4_journalled_write_end() will incorrectly attempt to write
to it, triggering a BUG_ON(pos + len > EXT4_I(inode)->i_inline_size) in
ext4_write_inline_data() since i_inline_size was not expanded.

Fix this by ensuring that ext4_journalled_write_end() only calls
ext4_write_inline_data_end() if the EXT4_STATE_MAY_INLINE_DATA flag is
set, mirroring the behavior of ext4_write_end() and ext4_da_write_end().
Comment 1 Keith Grant 2026-08-20 16:13:51 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026081551-CVE-2026-74308-60a2@gregkh/T