From: Andrey Ryabinin <aryabinin@virtuozzo.com>
Date: Tue, 17 Jul 2018 16:00:33 +0000 (+0300)
Subject: fuse: Don't access pipe->buffers without pipe_lock()
X-Git-Tag: Ubuntu-4.15.0-49.53~81
X-Git-Url: https://git.proxmox.com/?p=mirror_ubuntu-bionic-kernel.git;a=commitdiff_plain;h=3b3caf8ef9a669e82b59a9a4fec63cc2dd9391e8

fuse: Don't access pipe->buffers without pipe_lock()

BugLink: https://bugs.launchpad.net/bugs/1824553

fuse_dev_splice_write() reads pipe->buffers to determine the size of
'bufs' array before taking the pipe_lock(). This is not safe as
another thread might change the 'pipe->buffers' between the allocation
and taking the pipe_lock(). So we end up with too small 'bufs' array.

Move the bufs allocations inside pipe_lock()/pipe_unlock() to fix this.

Fixes: dd3bb14f44a6 ("fuse: support splice() writing to fuse device")
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: <stable@vger.kernel.org> # v2.6.35
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
(backported from commit a2477b0e67c52f4364a47c3ad70902bc2a61bd4c)
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
---

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index b1c3dd2eda01..d925d81e1525 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -1962,11 +1962,14 @@ static ssize_t fuse_dev_splice_write(struct pipe_inode_info *pipe,
 	if (!fud)
 		return -EPERM;
 
+	pipe_lock(pipe);
+
 	bufs = kmalloc(pipe->buffers * sizeof(struct pipe_buffer), GFP_KERNEL);
-	if (!bufs)
+	if (!bufs) {
+		pipe_unlock(pipe);
 		return -ENOMEM;
+	}
 
-	pipe_lock(pipe);
 	nbuf = 0;
 	rem = 0;
 	for (idx = 0; idx < pipe->nrbufs && rem < len; idx++)