From: Darrick J. Wong <djwong@xxxxxxxxxx>
For decades, Linux has never propagated O_EXCL into the user-visible
file flags in do_dentry_open:
f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
Therefore, one cannot use F_GETFL to determine if the file was opened
with O_EXCL. The unixfd IO manager will have to trust that the caller
opened the file in O_EXCL mode. Without this patch, the upcoming flock
patch will not work correctly in determining the lock mode to keep other
copies of fuse4fs and/or systemd from touching a fuse4fs mounted
filesystem.
Cc: <linux-ext4@xxxxxxxxxxxxxxx> # v1.43.2
Fixes: 4ccf9e4fe165cf ("libext2fs: add unixfd_io_manager")
Signed-off-by: "Darrick J. Wong" <djwong@xxxxxxxxxx>
---
lib/ext2fs/unix_io.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/lib/ext2fs/unix_io.c b/lib/ext2fs/unix_io.c
index e839628aa1b74d..55007ad7d2ae15 100644
--- a/lib/ext2fs/unix_io.c
+++ b/lib/ext2fs/unix_io.c
@@ -1172,11 +1172,10 @@ static errcode_t unixfd_open(const char *str_fd, int flags,
if (fd_flags == -1)
return EBADF;
- flags = 0;
+ /* O_EXCL is cleared by Linux at open and not returned by F_GETFL */
+ flags &= IO_FLAG_EXCLUSIVE;
if (fd_flags & O_RDWR)
flags |= IO_FLAG_RW;
- if (fd_flags & O_EXCL)
- flags |= IO_FLAG_EXCLUSIVE;
#if defined(O_DIRECT)
if (fd_flags & O_DIRECT)
flags |= IO_FLAG_DIRECT_IO;
