[PATCH 04/16] backing-file: use credential guards for writes
From: Christian Brauner <brauner@kernel.org>
Date: 2025-11-03 11:27:19
Also in:
cgroups, linux-cifs, linux-fsdevel, linux-nfs, linux-unionfs, lkml
Subsystem:
filesystems (vfs and infrastructure), filesystems [stackable], the rest · Maintainers:
Alexander Viro, Christian Brauner, Miklos Szeredi, Amir Goldstein, Linus Torvalds
Use credential guards for scoped credential override with automatic restoration on scope exit. Signed-off-by: Christian Brauner <brauner@kernel.org> --- fs/backing-file.c | 74 +++++++++++++++++++++++++++++-------------------------- 1 file changed, 39 insertions(+), 35 deletions(-)
diff --git a/fs/backing-file.c b/fs/backing-file.c
index 4cb7276e7ead..9bea737d5bef 100644
--- a/fs/backing-file.c
+++ b/fs/backing-file.c@@ -210,11 +210,47 @@ ssize_t backing_file_read_iter(struct file *file, struct iov_iter *iter, } EXPORT_SYMBOL_GPL(backing_file_read_iter); +static int do_backing_file_write_iter(struct file *file, struct iov_iter *iter, + struct kiocb *iocb, int flags, + void (*end_write)(struct kiocb *, ssize_t)) +{ + struct backing_aio *aio; + int ret; + + if (is_sync_kiocb(iocb)) { + rwf_t rwf = iocb_to_rw_flags(flags); + + ret = vfs_iter_write(file, iter, &iocb->ki_pos, rwf); + if (end_write) + end_write(iocb, ret); + return ret; + } + + ret = backing_aio_init_wq(iocb); + if (ret) + return ret; + + aio = kmem_cache_zalloc(backing_aio_cachep, GFP_KERNEL); + if (!aio) + return -ENOMEM; + + aio->orig_iocb = iocb; + aio->end_write = end_write; + kiocb_clone(&aio->iocb, iocb, get_file(file)); + aio->iocb.ki_flags = flags; + aio->iocb.ki_complete = backing_aio_queue_completion; + refcount_set(&aio->ref, 2); + ret = vfs_iocb_iter_write(file, &aio->iocb, iter); + backing_aio_put(aio); + if (ret != -EIOCBQUEUED) + backing_aio_cleanup(aio, ret); + return ret; +} + ssize_t backing_file_write_iter(struct file *file, struct iov_iter *iter, struct kiocb *iocb, int flags, struct backing_file_ctx *ctx) { - const struct cred *old_cred; ssize_t ret; if (WARN_ON_ONCE(!(file->f_mode & FMODE_BACKING)))
@@ -237,40 +273,8 @@ ssize_t backing_file_write_iter(struct file *file, struct iov_iter *iter, */ flags &= ~IOCB_DIO_CALLER_COMP; - old_cred = override_creds(ctx->cred); - if (is_sync_kiocb(iocb)) { - rwf_t rwf = iocb_to_rw_flags(flags); - - ret = vfs_iter_write(file, iter, &iocb->ki_pos, rwf); - if (ctx->end_write) - ctx->end_write(iocb, ret); - } else { - struct backing_aio *aio; - - ret = backing_aio_init_wq(iocb); - if (ret) - goto out; - - ret = -ENOMEM; - aio = kmem_cache_zalloc(backing_aio_cachep, GFP_KERNEL); - if (!aio) - goto out; - - aio->orig_iocb = iocb; - aio->end_write = ctx->end_write; - kiocb_clone(&aio->iocb, iocb, get_file(file)); - aio->iocb.ki_flags = flags; - aio->iocb.ki_complete = backing_aio_queue_completion; - refcount_set(&aio->ref, 2); - ret = vfs_iocb_iter_write(file, &aio->iocb, iter); - backing_aio_put(aio); - if (ret != -EIOCBQUEUED) - backing_aio_cleanup(aio, ret); - } -out: - revert_creds(old_cred); - - return ret; + with_creds(ctx->cred); + return do_backing_file_write_iter(file, iter, iocb, flags, ctx->end_write); } EXPORT_SYMBOL_GPL(backing_file_write_iter);
--
2.47.3