From: Jann Horn <jann@xxxxxxxxx>
This patch has been added to the 3.18 stable tree. If you have any
objections, please let us know.
===============
[ Upstream commit 4c17a6d56bb0cad3066a714e94f7185a24b40f49 ]
This might lead to local privilege escalation (code execution as
kernel) for systems where the following conditions are met:
- CONFIG_CIFS_SMB2 and CONFIG_CIFS_POSIX are enabled
- a cifs filesystem is mounted where:
- the mount option "vers" was used and set to a value >=2.0
- the attacker has write access to at least one file on the filesystem
To attack this, an attacker would have to guess the target_tcon
pointer (but guessing wrong doesn't cause a crash, it just returns an
error code) and win a narrow race.
CC: Stable <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Jann Horn <jann@xxxxxxxxx>
Signed-off-by: Steve French <smfrench@xxxxxxxxx>
Signed-off-by: Sasha Levin <sasha.levin@xxxxxxxxxx>
---
fs/cifs/ioctl.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/fs/cifs/ioctl.c b/fs/cifs/ioctl.c
index 8b7898b..64a9bca 100644
--- a/fs/cifs/ioctl.c
+++ b/fs/cifs/ioctl.c
@@ -67,6 +67,12 @@ static long cifs_ioctl_clone(unsigned int xid, struct file *dst_file,
goto out_drop_write;
}
+ if (src_file.file->f_op->unlocked_ioctl != cifs_ioctl) {
+ rc = -EBADF;
+ cifs_dbg(VFS, "src file seems to be from a different filesystem type\n");
+ goto out_fput;
+ }
+
if ((!src_file.file->private_data) || (!dst_file->private_data)) {
rc = -EBADF;
cifs_dbg(VFS, "missing cifsFileInfo on copy range src file\n");
--
2.1.4
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