Overview
In the Linux kernel, the following vulnerability has been resolved:
btrfs: do not double complete bio on errors during compressed reads
I hit some weird panics while fixing up the error handling from
btrfs_lookup_bio_sums(). Turns out the compression path will complete
the bio we use if we set up any of the compression bios and then return
an error, and then btrfs_submit_data_bio() will also call bio_endio() on
the bio.
Fix this by making btrfs_submit_compressed_read() responsible for
calling bio_endio() on the bio if there are any errors. Currently it
was only doing it if we created the compression bios, otherwise it was
depending on btrfs_submit_data_bio() to do the right thing. This
creates the above problem, so fix up btrfs_submit_compressed_read() to
always call bio_endio() in case of an error, and then simply return from
btrfs_submit_data_bio() if we had to call
btrfs_submit_compressed_read().