CVE-2025-40119

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> ext4: fix potential null deref in ext4_mb_init()<br /> <br /> In ext4_mb_init(), ext4_mb_avg_fragment_size_destroy() may be called<br /> when sbi-&gt;s_mb_avg_fragment_size remains uninitialized (e.g., if groupinfo<br /> slab cache allocation fails). Since ext4_mb_avg_fragment_size_destroy()<br /> lacks null pointer checking, this leads to a null pointer dereference.<br /> <br /> ==================================================================<br /> EXT4-fs: no memory for groupinfo slab cache<br /> BUG: kernel NULL pointer dereference, address: 0000000000000000<br /> PGD 0 P4D 0<br /> Oops: Oops: 0002 [#1] SMP PTI<br /> CPU:2 UID: 0 PID: 87 Comm:mount Not tainted 6.17.0-rc2 #1134 PREEMPT(none)<br /> RIP: 0010:_raw_spin_lock_irqsave+0x1b/0x40<br /> Call Trace:<br /> <br /> xa_destroy+0x61/0x130<br /> ext4_mb_init+0x483/0x540<br /> __ext4_fill_super+0x116d/0x17b0<br /> ext4_fill_super+0xd3/0x280<br /> get_tree_bdev_flags+0x132/0x1d0<br /> vfs_get_tree+0x29/0xd0<br /> do_new_mount+0x197/0x300<br /> __x64_sys_mount+0x116/0x150<br /> do_syscall_64+0x50/0x1c0<br /> entry_SYSCALL_64_after_hwframe+0x76/0x7e<br /> ==================================================================<br /> <br /> Therefore, add necessary null check to ext4_mb_avg_fragment_size_destroy()<br /> to prevent this issue. The same fix is also applied to<br /> ext4_mb_largest_free_orders_destroy().