CVE-2024-35784

Technical Description

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

btrfs: fix deadlock with fiemap and extent locking

While working on the patchset to remove extent locking I got a lockdep

splat with fiemap and pagefaulting with my new extent lock replacement

lock.

This deadlock exists with our normal code, we just don't have lockdep

annotations with the extent locking so we've never noticed it.

Since we're copying the fiemap extent to user space on every iteration

we have the chance of pagefaulting. Because we hold the extent lock for

the entire range we could mkwrite into a range in the file that we have

mmap'ed. This would deadlock with the following stack trace

[<0>] lock_extent+0x28d/0x2f0

[<0>] btrfs_page_mkwrite+0x273/0x8a0

[<0>] do_page_mkwrite+0x50/0xb0

[<0>] do_fault+0xc1/0x7b0

[<0>] __handle_mm_fault+0x2fa/0x460

[<0>] handle_mm_fault+0xa4/0x330

[<0>] do_user_addr_fault+0x1f4/0x800

[<0>] exc_page_fault+0x7c/0x1e0

[<0>] asm_exc_page_fault+0x26/0x30

[<0>] rep_movs_alter

Remediation

Check the references section for vendor advisories and patches from linux. Update linux_kernel to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

Affected Products

References