fs: avoid fdput() after failed fdget()

While debugging an unrelated problem, I noticed these two cases fdput() is called after failed fdget() while reviewing at all the fdget() and fdput() paths in the kernel.

Changes since v2:
Patches 1&2 changed to get rid of goto.

Changes since v1:
Patch 1:
Changed to address review comments to refine the code for improved readability in addition to the change to avoid fdput() on failed fdget()
Patch 2:
No change to v1. Including it in the series to keep the patches together.

Shuah Khan (2):
fs: avoid fdput() after failed fdget() in ksys_sync_file_range()
fs: avoid fdput() after failed fdget() in kernel_read_file_from_fd()

 fs/exec.c |  6 +++---
 fs/sync.c | 10 +++++-----
 2 files changed, 8 insertions(+), 8 deletions(-)

2.25.1

Fix ksys_sync_file_range() to avoid fdput() after a failed fdget(). fdput() doesn't do fput() on this file since FDPUT_FPUT isn't set in fd.flags.

Change it anyway since failed fdget() doesn't require a fdput(). Refine the code path a bit for it to read more clearly.
Reference: 22f96b3808c1 ("fs: add sync_file_range() helper")

---
 fs/sync.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

index 4d1ff010bc5a..3ec312bf62eb 100644
@@ -365,14 +365,14 @@ int ksys_sync_file_range(int fd, loff_t offset, loff_t nbytes,
 			 unsigned int flags)
 {
 	int ret;
-	struct fd f;
+	struct fd f = fdget(fd);
 
-	ret = -EBADF;
-	f = fdget(fd);
-	if (f.file)
-		ret = sync_file_range(f.file, offset, nbytes, flags);
+	if (!f.file)
+		return -EBADF;
 
+	ret = sync_file_range(f.file, offset, nbytes, flags);
 	fdput(f);
+
 	return ret;
 }
 

2.25.1

Luis

Fix kernel_read_file_from_fd() to avoid fdput() after a failed fdget(). fdput() doesn't do fput() on this file since FDPUT_FPUT isn't set in fd.flags. Fix it anyway since failed fdget() doesn't require a fdput().

This was introduced in a commit that added kernel_read_file_from_fd() as a wrapper for the VFS common kernel_read_file().

---
 fs/exec.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

index 06b4c550af5d..16a3d3192d6a 100644
@@ -1015,14 +1015,14 @@ int kernel_read_file_from_fd(int fd, void **buf, loff_t *size, loff_t max_size,
 			     enum kernel_read_file_id id)
 {
 	struct fd f = fdget(fd);
-	int ret = -EBADF;
+	int ret;
 
 	if (!f.file)
-		goto out;
+		return -EBADF;
 
 	ret = kernel_read_file(f.file, buf, size, max_size, id);
-out:
 	fdput(f);
+
 	return ret;
 }
 EXPORT_SYMBOL_GPL(kernel_read_file_from_fd);

2.25.1

Thanks, Shuah.