linux-ext4 - [PATCH 13/13] ext4_get_link(): fix breakage in RCU mode

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Message-Id: <20240204021739.1157830-13-viro@zeniv.linux.org.uk>
Date: Sun,  4 Feb 2024 02:17:39 +0000
From: Al Viro <viro@...iv.linux.org.uk>
To: linux-fsdevel@...r.kernel.org
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
	Christian Brauner <brauner@...nel.org>,
	linux-ext4@...r.kernel.org,
	linux-nfs@...r.kernel.org,
	Miklos Szeredi <miklos@...redi.hu>,
	linux-cifs@...r.kernel.org
Subject: [PATCH 13/13] ext4_get_link(): fix breakage in RCU mode

1) errors from ext4_getblk() should not be propagated to caller
unless we are really sure that we would've gotten the same error
in non-RCU pathwalk.
2) we leak buffer_heads if ext4_getblk() is successful, but bh is
not uptodate.

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
---
 fs/ext4/symlink.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/fs/ext4/symlink.c b/fs/ext4/symlink.c
index 75bf1f88843c..645240cc0229 100644
--- a/fs/ext4/symlink.c
+++ b/fs/ext4/symlink.c
@@ -92,10 +92,12 @@ static const char *ext4_get_link(struct dentry *dentry, struct inode *inode,
 
 	if (!dentry) {
 		bh = ext4_getblk(NULL, inode, 0, EXT4_GET_BLOCKS_CACHED_NOWAIT);
-		if (IS_ERR(bh))
-			return ERR_CAST(bh);
-		if (!bh || !ext4_buffer_uptodate(bh))
+		if (IS_ERR(bh) || !bh)
 			return ERR_PTR(-ECHILD);
+		if (!ext4_buffer_uptodate(bh)) {
+			brelse(bh);
+			return ERR_PTR(-ECHILD);
+		}
 	} else {
 		bh = ext4_bread(NULL, inode, 0, 0);
 		if (IS_ERR(bh))
-- 
2.39.2