CVE-2022-50344

ext4: fix null-ptr-deref in ext4_write_info

State: Published
Severity: 5.5 Medium
Published: Sep 16, 2025
Updated: May 11, 2026
Reserved: Sep 16, 2025

Description

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

ext4: fix null-ptr-deref in ext4_write_info

I caught a null-ptr-deref bug as follows: ================================================================== KASAN: null-ptr-deref in range [0x0000000000000068-0x000000000000006f] CPU: 1 PID: 1589 Comm: umount Not tainted 5.10.0-02219-dirty #339 RIP: 0010:ext4_write_info+0x53/0x1b0 [...] Call Trace: dquot_writeback_dquots+0x341/0x9a0 ext4_sync_fs+0x19e/0x800 __sync_filesystem+0x83/0x100 sync_filesystem+0x89/0xf0 generic_shutdown_super+0x79/0x3e0 kill_block_super+0xa1/0x110 deactivate_locked_super+0xac/0x130 deactivate_super+0xb6/0xd0 cleanup_mnt+0x289/0x400 __cleanup_mnt+0x16/0x20 task_work_run+0x11c/0x1c0 exit_to_user_mode_prepare+0x203/0x210 syscall_exit_to_user_mode+0x5b/0x3a0 do_syscall_64+0x59/0x70 entry_SYSCALL_64_after_hwframe+0x44/0xa9 ==================================================================

Above issue may happen as follows: ------------------------------------- exit_to_user_mode_prepare task_work_run __cleanup_mnt cleanup_mnt deactivate_super deactivate_locked_super kill_block_super generic_shutdown_super shrink_dcache_for_umount dentry = sb->s_root sb->s_root = NULL <--- Here set NULL sync_filesystem __sync_filesystem sb->s_op->sync_fs > ext4_sync_fs dquot_writeback_dquots sb->dq_op->write_info > ext4_write_info ext4_journal_start(d_inode(sb->s_root), EXT4_HT_QUOTA, 2) d_inode(sb->s_root) s_root->d_inode <--- Null pointer dereference

To solve this problem, we use ext4_journal_start_sb directly to avoid s_root being used.

Scores

CVSS	Score	Vector	Source
3.1	5.5 Medium	CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H	CISA-ADP

Weaknesses

CWE-476 NULL Pointer Dereference

Affected Products

Product	Versions
LinuxLinux	a1177825719ccef3f76ef39bbfd5ebb6087d53c7 to before dc451578446afd03c0c21913993c08898a691435Affected a1177825719ccef3f76ef39bbfd5ebb6087d53c7 to before f4b5ff0b794aa94afac7269c494550ca2f66511bAffected a1177825719ccef3f76ef39bbfd5ebb6087d53c7 to before 947264e00c46de19a016fd81218118c708fed2f3Affected a1177825719ccef3f76ef39bbfd5ebb6087d53c7 to before 3638aa1c7d87c0ca0aef23cf58cae2c48e7daca4Affected a1177825719ccef3f76ef39bbfd5ebb6087d53c7 to before f34ab95162763cd7352f46df169296eec28b688dAffected a1177825719ccef3f76ef39bbfd5ebb6087d53c7 to before 533c60a0b97cee5daab376933f486207e6680fb7Affected a1177825719ccef3f76ef39bbfd5ebb6087d53c7 to before 4a657319cfabd6199fd0b7b65bbebf6ded7a11c1Affected a1177825719ccef3f76ef39bbfd5ebb6087d53c7 to before bb420e8afc854d2a1caaa23a0c129839acfb7888Affected a1177825719ccef3f76ef39bbfd5ebb6087d53c7 to before f9c1f248607d5546075d3f731e7607d5571f2b60Affected
LinuxLinux	3.6Affected before 3.6Not affected 4.9.331 through 4.9.Not affected 4.14.296 through 4.14.Not affected 4.19.262 through 4.19.Not affected 5.4.220 through 5.4.Not affected 5.10.150 through 5.10.Not affected 5.15.75 through 5.15.Not affected 5.19.17 through 5.19.Not affected 6.0.3 through 6.0.Not affected 6.1 and laterNot affected

Product

Versions

LinuxLinux

a1177825719ccef3f76ef39bbfd5ebb6087d53c7 to before dc451578446afd03c0c21913993c08898a691435Affected
a1177825719ccef3f76ef39bbfd5ebb6087d53c7 to before f4b5ff0b794aa94afac7269c494550ca2f66511bAffected
a1177825719ccef3f76ef39bbfd5ebb6087d53c7 to before 947264e00c46de19a016fd81218118c708fed2f3Affected
a1177825719ccef3f76ef39bbfd5ebb6087d53c7 to before 3638aa1c7d87c0ca0aef23cf58cae2c48e7daca4Affected
a1177825719ccef3f76ef39bbfd5ebb6087d53c7 to before f34ab95162763cd7352f46df169296eec28b688dAffected
a1177825719ccef3f76ef39bbfd5ebb6087d53c7 to before 533c60a0b97cee5daab376933f486207e6680fb7Affected
a1177825719ccef3f76ef39bbfd5ebb6087d53c7 to before 4a657319cfabd6199fd0b7b65bbebf6ded7a11c1Affected
a1177825719ccef3f76ef39bbfd5ebb6087d53c7 to before bb420e8afc854d2a1caaa23a0c129839acfb7888Affected
a1177825719ccef3f76ef39bbfd5ebb6087d53c7 to before f9c1f248607d5546075d3f731e7607d5571f2b60Affected

LinuxLinux

3.6Affected
before 3.6Not affected
4.9.331 through 4.9.*Not affected
4.14.296 through 4.14.*Not affected
4.19.262 through 4.19.*Not affected
5.4.220 through 5.4.*Not affected
5.10.150 through 5.10.*Not affected
5.15.75 through 5.15.*Not affected
5.19.17 through 5.19.*Not affected
6.0.3 through 6.0.*Not affected
6.1 and laterNot affected

References

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