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nfs/localio: fix regression due to out-of-order __put_cred 

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>
This commit is contained in:
Mike Snitzer 2025-11-26 01:01:25 -05:00 committed by Linus Torvalds
parent 11efc1cb70
commit 3af870aedb
1 changed files with 17 additions and 31 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

48
fs/nfs/localio.c
View File

@ -615,8 +615,11 @@ static void nfs_local_read_aio_complete(struct kiocb *kiocb, long ret)
nfs_local_pgio_aio_complete(iocb); /* Calls nfs_local_read_aio_complete_work */
}
static void do_nfs_local_call_read(struct nfs_local_kiocb *iocb, struct file *filp)
static void nfs_local_call_read(struct work_struct *work)
{
struct nfs_local_kiocb *iocb =
container_of(work, struct nfs_local_kiocb, work);
struct file *filp = iocb->kiocb.ki_filp;
bool force_done = false;
ssize_t status;
int n_iters;
@ -633,7 +636,9 @@ static void do_nfs_local_call_read(struct nfs_local_kiocb *iocb, struct file *fi
} else
iocb->kiocb.ki_flags &= ~IOCB_DIRECT;
status = filp->f_op->read_iter(&iocb->kiocb, &iocb->iters[i]);
scoped_with_creds(filp->f_cred)
status = filp->f_op->read_iter(&iocb->kiocb, &iocb->iters[i]);
if (status != -EIOCBQUEUED) {
if (unlikely(status >= 0 && status < iocb->iters[i].count))
force_done = true; /* Partial read */
@ -645,16 +650,6 @@ static void do_nfs_local_call_read(struct nfs_local_kiocb *iocb, struct file *fi
}
}
static void nfs_local_call_read(struct work_struct *work)
{
struct nfs_local_kiocb *iocb =
container_of(work, struct nfs_local_kiocb, work);
struct file *filp = iocb->kiocb.ki_filp;
scoped_with_creds(filp->f_cred)
do_nfs_local_call_read(iocb, filp);
}
static int
nfs_local_do_read(struct nfs_local_kiocb *iocb,
const struct rpc_call_ops *call_ops)
@ -822,13 +817,18 @@ static void nfs_local_write_aio_complete(struct kiocb *kiocb, long ret)
nfs_local_pgio_aio_complete(iocb); /* Calls nfs_local_write_aio_complete_work */
}
static ssize_t do_nfs_local_call_write(struct nfs_local_kiocb *iocb,
struct file *filp)
static void nfs_local_call_write(struct work_struct *work)
{
struct nfs_local_kiocb *iocb =
container_of(work, struct nfs_local_kiocb, work);
struct file *filp = iocb->kiocb.ki_filp;
unsigned long old_flags = current->flags;
bool force_done = false;
ssize_t status;
int n_iters;
current->flags |= PF_LOCAL_THROTTLE | PF_MEMALLOC_NOIO;
file_start_write(filp);
n_iters = atomic_read(&iocb->n_iters);
for (int i = 0; i < n_iters ; i++) {
@ -842,7 +842,9 @@ static ssize_t do_nfs_local_call_write(struct nfs_local_kiocb *iocb,
} else
iocb->kiocb.ki_flags &= ~IOCB_DIRECT;
status = filp->f_op->write_iter(&iocb->kiocb, &iocb->iters[i]);
scoped_with_creds(filp->f_cred)
status = filp->f_op->write_iter(&iocb->kiocb, &iocb->iters[i]);
if (status != -EIOCBQUEUED) {
if (unlikely(status >= 0 && status < iocb->iters[i].count))
force_done = true; /* Partial write */
@ -854,22 +856,6 @@ static ssize_t do_nfs_local_call_write(struct nfs_local_kiocb *iocb,
}
file_end_write(filp);
return status;
}
static void nfs_local_call_write(struct work_struct *work)
{
struct nfs_local_kiocb *iocb =
container_of(work, struct nfs_local_kiocb, work);
struct file *filp = iocb->kiocb.ki_filp;
unsigned long old_flags = current->flags;
ssize_t status;
current->flags |= PF_LOCAL_THROTTLE | PF_MEMALLOC_NOIO;
scoped_with_creds(filp->f_cred)
status = do_nfs_local_call_write(iocb, filp);
current->flags = old_flags;
}