linux-kernel - [PATCH v2 1/2] fs: avoid fdput() after failed fdget() in ksys_sync_file

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Message-Id: <71cc3966f60f884924f9dff8875ed478e858dca1.1589311577.git.skhan@linuxfoundation.org>
Date:   Tue, 12 May 2020 13:43:04 -0600
From:   Shuah Khan <skhan@...uxfoundation.org>
To:     viro@...iv.linux.org.uk, axboe@...nel.dk, zohar@...ux.vnet.ibm.com,
        mcgrof@...nel.org, keescook@...omium.org
Cc:     Shuah Khan <skhan@...uxfoundation.org>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 1/2] fs: avoid fdput() after failed fdget() in ksys_sync_file_range()

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: commit 22f96b3808c1 ("fs: add sync_file_range() helper")

Signed-off-by: Shuah Khan <skhan@...uxfoundation.org>
---
 fs/sync.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/fs/sync.c b/fs/sync.c
index 4d1ff010bc5a..300ca73ec87c 100644
--- a/fs/sync.c
+++ b/fs/sync.c
@@ -364,15 +364,15 @@ int sync_file_range(struct file *file, loff_t offset, loff_t nbytes,
 int ksys_sync_file_range(int fd, loff_t offset, loff_t nbytes,
 			 unsigned int flags)
 {
-	int ret;
-	struct fd f;
+	int ret = -EBADF;
+	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)
+		goto out;
 
+	ret = sync_file_range(f.file, offset, nbytes, flags);
 	fdput(f);
+out:
 	return ret;
 }
 
-- 
2.25.1