linux-ext4 - [PATCH 02/12] fuse2fs: fix readlink failure

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <175573318640.4130038.13924482444671815931.stgit@frogsfrogsfrogs>
Date: Wed, 20 Aug 2025 16:41:23 -0700
From: "Darrick J. Wong" <djwong@...nel.org>
To: tytso@....edu
Cc: linux-ext4@...r.kernel.org, linux-ext4@...r.kernel.org
Subject: [PATCH 02/12] fuse2fs: fix readlink failure

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

For readlink of slow symlinks, an IO error when reading the link target
cause memory corruption.  This happens because the error case for
ext2fs_file_read closes the file, translates the error, but then jumps
down to the regular termination code, which re-closes the file and is
hence a UAF.  Straighten out the error paths to eliminate the UAF.
Also fix the bug that short target reads aren't flagged as corruption
as is done in the kernel.

Cc: <linux-ext4@...r.kernel.org> # v1.43
Fixes: 81cbf1ef4f5dab ("misc: add fuse2fs, a FUSE server for e2fsprogs")
Signed-off-by: "Darrick J. Wong" <djwong@...nel.org>
---
 misc/fuse2fs.c |    8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/misc/fuse2fs.c b/misc/fuse2fs.c
index 4d42a634bf377b..f9da9c1ac051cb 100644
--- a/misc/fuse2fs.c
+++ b/misc/fuse2fs.c
@@ -1086,13 +1086,11 @@ static int op_readlink(const char *path, char *buf, size_t len)
 		}

 		err = ext2fs_file_read(file, buf, len, &got);
-		if (err || got != len) {
-			ext2fs_file_close(file);
+		if (err)
 			ret = translate_error(fs, ino, err);
-			goto out2;
-		}
+		else if (got != len)
+			ret = translate_error(fs, ino, EXT2_ET_INODE_CORRUPTED);

-out2:
 		err = ext2fs_file_close(file);
 		if (ret)
 			goto out;