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Subject[PATCH v2] vfs: fix bug when opening a file with O_DIRECT on a file system that does not support it will leave an empty file
Date
Colin Ian King reported the following

1. create a minix file system and mount it
2. open a file on the file system with O_RDWR | O_CREAT | O_TRUNC | O_DIRECT
3. open fails with -EINVAL but leaves an empty file behind. All other open() failures don't leave the
failed open files behind.

The reason is because when checking the O_DIRECT in do_dentry_open, the inode has created, and later err
processing can't remove the inode.

The patch will remove the file in last step of open in do_open().

Signed-off-by: Qinghua Jin <qhjin.dev@gmail.com>
Reported-by: Colin Ian King <colin.king@canonical.com>
---
fs/namei.c | 6 ++++++
fs/open.c | 6 ------
2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 1f9d2187c765..081feb804154 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3426,6 +3426,12 @@ static int do_open(struct nameidata *nd,
error = vfs_open(&nd->path, file);
if (!error)
error = ima_file_check(file, op->acc_mode);
+ if (!error && (file->f_flags & O_DIRECT)) {
+ if (!file->f_mapping->a_ops || !file->f_mapping->a_ops->direct_IO) {
+ do_unlinkat(AT_FDCWD, getname_kernel(nd->name->name));
+ return -EINVAL;
+ }
+ }
if (!error && do_truncate)
error = handle_truncate(mnt_userns, file);
if (unlikely(error > 0)) {
diff --git a/fs/open.c b/fs/open.c
index f732fb94600c..2829c3613c0f 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -838,12 +838,6 @@ static int do_dentry_open(struct file *f,

file_ra_state_init(&f->f_ra, f->f_mapping->host->i_mapping);

- /* NB: we're sure to have correct a_ops only after f_op->open */
- if (f->f_flags & O_DIRECT) {
- if (!f->f_mapping->a_ops || !f->f_mapping->a_ops->direct_IO)
- return -EINVAL;
- }
-
/*
* XXX: Huge page cache doesn't support writing yet. Drop all page
* cache for this file before processing writes.
--
2.30.2
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