Commit f2060bdc21 ("nfs/localio: add refcounting for each iocb IO
associated with NFS pgio header") inadvertantly reintroduced the same
potential for __put_cred() triggering BUG_ON(cred == current->cred) that
commit 992203a1fb ("nfs/localio: restore creds before releasing pageio
data") fixed.
Fix this by saving and restoring the cred around each {read,write}_iter
call within the respective for loop of nfs_local_call_{read,write} using
scoped_with_creds().
NOTE: this fix started by first reverting the following commits:
94afb627df ("nfs: use credential guards in nfs_local_call_read()")
bff3c841f7 ("nfs: use credential guards in nfs_local_call_write()")
1d18101a64 ("Merge tag 'kernel-6.19-rc1.cred' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs")
followed by narrowly fixing the cred lifetime issue by using
scoped_with_creds(). In doing so, this commit's changes appear more
extensive than they really are (as evidenced by comparing to v6.18's
fs/nfs/localio.c).
Reported-by: Zorro Lang <zlang@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Acked-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Link: https://lore.kernel.org/linux-next/20251205111942.4150b06f@canb.auug.org.au/
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
3af870aedb