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

erofs: reliably distinguish block based and fscache mode

When erofs_kill_sb() is called in block dev based mode, s_bdev may not have been initialised yet, and if CONFIG_EROFS_FS_ONDEMAND is enabled, it will be mistaken for fscache mode, and then attempt to free an anon_dev that has never been allocated, triggering the following warning:

============================================ ida_free called for id=0 which is not allocated. WARNING: CPU: 14 PID: 926 at lib/idr.c:525 ida_free+0x134/0x140 Modules linked in: CPU: 14 PID: 926 Comm: mount Not tainted 6.9.0-rc3-dirty #630 RIP: 0010:ida_free+0x134/0x140 Call Trace: erofs_kill_sb+0x81/0x90 deactivate_locked_super+0x35/0x80 get_tree_bdev+0x136/0x1e0 vfs_get_tree+0x2c/0xf0 do_new_mount+0x190/0x2f0 […]

Now when erofs_kill_sb() is called, erofs_sb_info must have been initialised, so use sbi->fsid to distinguish between the two modes.

Weakness

The product accesses or uses a pointer that has not been initialized.

Affected Software

Extended Description

If the pointer contains an uninitialized value, then the value might not point to a valid memory location. This could cause the product to read from or write to unexpected memory locations, leading to a denial of service. If the uninitialized pointer is used as a function call, then arbitrary functions could be invoked. If an attacker can influence the portion of uninitialized memory that is contained in the pointer, this weakness could be leveraged to execute code or perform other attacks. Depending on memory layout, associated memory management behaviors, and product operation, the attacker might be able to influence the contents of the uninitialized pointer, thus gaining more fine-grained control of the memory location to be accessed.

References

• https://git.kernel.org/stable/c/7af2ae1b1531feab5d38ec9c8f472dc6cceb4606
• https://git.kernel.org/stable/c/dcdd49701e429c55b3644fd70fc58d85745f8cfe
• https://git.kernel.org/stable/c/f9b877a7ee312ec8ce17598a7ef85cb820d7c371
• https://git.kernel.org/stable/c/7af2ae1b1531feab5d38ec9c8f472dc6cceb4606
• https://git.kernel.org/stable/c/dcdd49701e429c55b3644fd70fc58d85745f8cfe
• https://git.kernel.org/stable/c/f9b877a7ee312ec8ce17598a7ef85cb820d7c371