linux-kernel - [PATCH 4.4 069/118] fuse: direct-io: dont dirty ITER

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: <20160922172942.191827060@linuxfoundation.org>
Date:   Thu, 22 Sep 2016 19:29:29 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Sheng Yang <sheng@...ker.org>,
        Miklos Szeredi <mszeredi@...hat.com>,
        Ashish Samant <ashish.samant@...cle.com>
Subject: [PATCH 4.4 069/118] fuse: direct-io: dont dirty ITER_BVEC pages

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Miklos Szeredi <mszeredi@...hat.com>

commit 8fba54aebbdf1f999738121922e74bf796ad60ee upstream.

When reading from a loop device backed by a fuse file it deadlocks on
lock_page().

This is because the page is already locked by the read() operation done on
the loop device.  In this case we don't want to either lock the page or
dirty it.

So do what fs/direct-io.c does: only dirty the page for ITER_IOVEC vectors.

Reported-by: Sheng Yang <sheng@...ker.org>
Fixes: aa4d86163e4e ("block: loop: switch to VFS ITER_BVEC")
Signed-off-by: Miklos Szeredi <mszeredi@...hat.com>
Reviewed-by: Sheng Yang <sheng@...ker.org>
Reviewed-by: Ashish Samant <ashish.samant@...cle.com>
Tested-by: Sheng Yang <sheng@...ker.org>
Tested-by: Ashish Samant <ashish.samant@...cle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/fuse/file.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -540,13 +540,13 @@ void fuse_read_fill(struct fuse_req *req
 	req->out.args[0].size = count;
 }
 
-static void fuse_release_user_pages(struct fuse_req *req, int write)
+static void fuse_release_user_pages(struct fuse_req *req, bool should_dirty)
 {
 	unsigned i;
 
 	for (i = 0; i < req->num_pages; i++) {
 		struct page *page = req->pages[i];
-		if (write)
+		if (should_dirty)
 			set_page_dirty_lock(page);
 		put_page(page);
 	}
@@ -1331,6 +1331,7 @@ ssize_t fuse_direct_io(struct fuse_io_pr
 		       loff_t *ppos, int flags)
 {
 	int write = flags & FUSE_DIO_WRITE;
+	bool should_dirty = !write && iter_is_iovec(iter);
 	int cuse = flags & FUSE_DIO_CUSE;
 	struct file *file = io->file;
 	struct inode *inode = file->f_mapping->host;
@@ -1375,7 +1376,7 @@ ssize_t fuse_direct_io(struct fuse_io_pr
 			nres = fuse_send_read(req, io, pos, nbytes, owner);
 
 		if (!io->async)
-			fuse_release_user_pages(req, !write);
+			fuse_release_user_pages(req, should_dirty);
 		if (req->out.h.error) {
 			if (!res)
 				res = req->out.h.error;