CVE-2022-49761

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

btrfs: always report error in run_one_delayed_ref()

Currently we have a btrfs_debug() for run_one_delayed_ref() failure, but if end users hit such problem, there will be no chance that btrfs_debug() is enabled. This can lead to very little useful info for debugging.

This patch will:

• Add extra info for error reporting Including:

  • logical bytenr
  • num_bytes
  • type
  • action
  • ref_mod

• Replace the btrfs_debug() with btrfs_err()

• Move the error reporting into run_one_delayed_ref() This is to avoid use-after-free, the @node can be freed in the caller.

This error should only be triggered at most once.

As if run_one_delayed_ref() failed, we trigger the error message, then causing the call chain to error out:

btrfs_run_delayed_refs() - btrfs_run_delayed_refs() - btrfs_run_delayed_refs_for_head() `- run_one_delayed_ref()

And we will abort the current transaction in btrfs_run_delayed_refs(). If we have to run delayed refs for the abort transaction, run_one_delayed_ref() will just cleanup the refs and do nothing, thus no new error messages would be output.

Weakness

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.

Affected Software

Potential Mitigations

References

• https://git.kernel.org/stable/c/18bd1c9c02e64a3567f90c83c2c8b855531c8098
• https://git.kernel.org/stable/c/39f501d68ec1ed5cd5c66ac6ec2a7131c517bb92
• https://git.kernel.org/stable/c/853ffa1511b058c79a4c9bb1407b3b20ce311792
• https://git.kernel.org/stable/c/fdb4a70bb768d2a87890409597529ad81cb3de8a