[PATCH 1/2] libext2fs: use F_GETFL, not F_GETFD, in unixfd_open

[PATCH 1/2] libext2fs: use F_GETFL, not F_GETFD, in unixfd_open

[Darrick J. Wong]

From: Darrick J. Wong <djwong@kernel.org>

F_GETFD is the fcntl command that returns FD_* flags, but the callsite
wants to look at the O_* flags.  F_GETFL is the fcntl command that
returns the O_* flags, so change the subcommand to be correct.

Cc: <linux-ext4@vger.kernel.org> # v1.43.2
Fixes: 4ccf9e4fe165cf ("libext2fs: add unixfd_io_manager")
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
---
 lib/ext2fs/unix_io.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/ext2fs/unix_io.c b/lib/ext2fs/unix_io.c
index 4a841f7f2133d4..e839628aa1b74d 100644
--- a/lib/ext2fs/unix_io.c
+++ b/lib/ext2fs/unix_io.c
@@ -1168,7 +1168,7 @@ static errcode_t unixfd_open(const char *str_fd, int flags,
 
 	fd = atoi(str_fd);
 #if defined(HAVE_FCNTL)
-	fd_flags = fcntl(fd, F_GETFD);
+	fd_flags = fcntl(fd, F_GETFL);
 	if (fd_flags == -1)
 		return EBADF;
 

[PATCH 2/2] libext2fs: don't look for O_EXCL in the F_GETFL output

[Darrick J. Wong]

From: Darrick J. Wong <djwong@kernel.org>

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@vger.kernel.org> # v1.43.2
Fixes: 4ccf9e4fe165cf ("libext2fs: add unixfd_io_manager")
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
---
 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;