6.18-stable review patch. If anyone has any objections, please let me know.
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From: Mike Snitzer snitzer@kernel.org
commit 3af870aedbff10bfed220e280b57a405e972229f upstream.
Commit f2060bdc21d7 ("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 992203a1fba5 ("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:
94afb627dfc2 ("nfs: use credential guards in nfs_local_call_read()") bff3c841f7bd ("nfs: use credential guards in nfs_local_call_write()") 1d18101a644e ("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 Signed-off-by: Trond Myklebust trond.myklebust@hammerspace.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/nfs/localio.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-)
--- a/fs/nfs/localio.c +++ b/fs/nfs/localio.c @@ -623,8 +623,6 @@ static void nfs_local_call_read(struct w ssize_t status; int n_iters;
- save_cred = override_creds(filp->f_cred); - n_iters = atomic_read(&iocb->n_iters); for (int i = 0; i < n_iters ; i++) { if (iocb->iter_is_dio_aligned[i]) { @@ -637,7 +635,10 @@ static void nfs_local_call_read(struct w } else iocb->kiocb.ki_flags &= ~IOCB_DIRECT;
+ save_cred = override_creds(filp->f_cred); status = filp->f_op->read_iter(&iocb->kiocb, &iocb->iters[i]); + revert_creds(save_cred); + if (status != -EIOCBQUEUED) { if (unlikely(status >= 0 && status < iocb->iters[i].count)) force_done = true; /* Partial read */ @@ -647,8 +648,6 @@ static void nfs_local_call_read(struct w } } } - - revert_creds(save_cred); }
static int @@ -830,7 +829,6 @@ static void nfs_local_call_write(struct int n_iters;
current->flags |= PF_LOCAL_THROTTLE | PF_MEMALLOC_NOIO; - save_cred = override_creds(filp->f_cred);
file_start_write(filp); n_iters = atomic_read(&iocb->n_iters); @@ -845,7 +843,10 @@ static void nfs_local_call_write(struct } else iocb->kiocb.ki_flags &= ~IOCB_DIRECT;
+ save_cred = override_creds(filp->f_cred); status = filp->f_op->write_iter(&iocb->kiocb, &iocb->iters[i]); + revert_creds(save_cred); + if (status != -EIOCBQUEUED) { if (unlikely(status >= 0 && status < iocb->iters[i].count)) force_done = true; /* Partial write */ @@ -857,7 +858,6 @@ static void nfs_local_call_write(struct } file_end_write(filp);
- revert_creds(save_cred); current->flags = old_flags; }