CVE-2024-26773

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

ext4: avoid allocating blocks from corrupted group in ext4_mb_try_best_found()

Determine if the group block bitmap is corrupted before using ac_b_ex in

ext4_mb_try_best_found() to avoid allocating blocks from a group with a

corrupted block bitmap in the following concurrency and making the

situation worse.

ext4_mb_regular_allocator

ext4_lock_group(sb, group)

ext4_mb_good_group

// check if the group bbitmap is corrupted

ext4_mb_complex_scan_group

// Scan group gets ac_b_ex but doesn't use it

ext4_unlock_group(sb, group)

ext4_mark_group_bitmap_corrupted(group)

// The block bitmap was corrupted during

// the group unlock gap.

ext4_mb_try_best_found

ext4_lock_group(ac->ac_sb, group)

ext4_mb_use_best_found

mb_mark_used

// Allocating blocks in block bitmap corrupted group