[PATCH] netfs: Fix AIO error handling when doing write-through

[Christian Brauner]

On Tue, 21 May 2024 14:36:27 +0100, David Howells wrote:
> If an error occurs whilst we're doing an AIO write in write-through mode,
> we may end up calling ->ki_complete() *and* returning an error from
> ->write_iter().  This can result in either a UAF (the ->ki_complete() func
> pointer may get overwritten, for example) or a refcount underflow in
> io_submit() as ->ki_complete is called twice.
> 
> Fix this by making netfs_end_writethrough() - and thus
> netfs_perform_write() - unconditionally return -EIOCBQUEUED if we're doing
> an AIO write and wait for completion if we're not.
> 
> [...]

Applied to the vfs.fixes branch of the vfs/vfs.git tree.
Patches in the vfs.fixes branch should appear in linux-next soon.

Please report any outstanding bugs that were missed during review in a
new review to the original patch series allowing us to drop it.

It's encouraged to provide Acked-bys and Reviewed-bys even though the
patch has now been applied. If possible patch trailers will be updated.

Note that commit hashes shown below are subject to change due to rebase,
trailer updates or similar. If in doubt, please check the listed branch.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git
branch: vfs.fixes

[1/1] netfs: Fix AIO error handling when doing write-through
      https://git.kernel.org/vfs/vfs/c/eb5239732070