Patch "netfs: Fix enomem handling in buffered reads" has been added to the 6.12-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    netfs: Fix enomem handling in buffered reads

to the 6.12-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     netfs-fix-enomem-handling-in-buffered-reads.patch
and it can be found in the queue-6.12 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 79ca233017cd28e3e5016ea9037225491c45bb43
Author: David Howells <dhowells@xxxxxxxxxx>
Date:   Fri Dec 13 13:50:03 2024 +0000

    netfs: Fix enomem handling in buffered reads
    
    [ Upstream commit 105549d09a539a876b7c3330ab52d8aceedad358 ]
    
    If netfs_read_to_pagecache() gets an error from either ->prepare_read() or
    from netfs_prepare_read_iterator(), it needs to decrement ->nr_outstanding,
    cancel the subrequest and break out of the issuing loop.  Currently, it
    only does this for two of the cases, but there are two more that aren't
    handled.
    
    Fix this by moving the handling to a common place and jumping to it from
    all four places.  This is in preference to inserting a wrapper around
    netfs_prepare_read_iterator() as proposed by Dmitry Antipov[1].
    
    Link: https://lore.kernel.org/r/20241202093943.227786-1-dmantipov@xxxxxxxxx/ [1]
    
    Fixes: ee4cdf7ba857 ("netfs: Speed up buffered reading")
    Reported-by: syzbot+404b4b745080b6210c6c@xxxxxxxxxxxxxxxxxxxxxxxxx
    Closes: https://syzkaller.appspot.com/bug?extid=404b4b745080b6210c6c
    Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/20241213135013.2964079-4-dhowells@xxxxxxxxxx
    Tested-by: syzbot+404b4b745080b6210c6c@xxxxxxxxxxxxxxxxxxxxxxxxx
    cc: Dmitry Antipov <dmantipov@xxxxxxxxx>
    cc: Jeff Layton <jlayton@xxxxxxxxxx>
    cc: netfs@xxxxxxxxxxxxxxx
    cc: linux-fsdevel@xxxxxxxxxxxxxxx
    Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/fs/netfs/buffered_read.c b/fs/netfs/buffered_read.c
index af46a598f4d7..2dd2260352db 100644
--- a/fs/netfs/buffered_read.c
+++ b/fs/netfs/buffered_read.c
@@ -275,22 +275,14 @@ static void netfs_read_to_pagecache(struct netfs_io_request *rreq)
 			netfs_stat(&netfs_n_rh_download);
 			if (rreq->netfs_ops->prepare_read) {
 				ret = rreq->netfs_ops->prepare_read(subreq);
-				if (ret < 0) {
-					atomic_dec(&rreq->nr_outstanding);
-					netfs_put_subrequest(subreq, false,
-							     netfs_sreq_trace_put_cancel);
-					break;
-				}
+				if (ret < 0)
+					goto prep_failed;
 				trace_netfs_sreq(subreq, netfs_sreq_trace_prepare);
 			}
 
 			slice = netfs_prepare_read_iterator(subreq);
-			if (slice < 0) {
-				atomic_dec(&rreq->nr_outstanding);
-				netfs_put_subrequest(subreq, false, netfs_sreq_trace_put_cancel);
-				ret = slice;
-				break;
-			}
+			if (slice < 0)
+				goto prep_iter_failed;
 
 			rreq->netfs_ops->issue_read(subreq);
 			goto done;
@@ -302,6 +294,8 @@ static void netfs_read_to_pagecache(struct netfs_io_request *rreq)
 			trace_netfs_sreq(subreq, netfs_sreq_trace_submit);
 			netfs_stat(&netfs_n_rh_zero);
 			slice = netfs_prepare_read_iterator(subreq);
+			if (slice < 0)
+				goto prep_iter_failed;
 			__set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
 			netfs_read_subreq_terminated(subreq, 0, false);
 			goto done;
@@ -310,6 +304,8 @@ static void netfs_read_to_pagecache(struct netfs_io_request *rreq)
 		if (source == NETFS_READ_FROM_CACHE) {
 			trace_netfs_sreq(subreq, netfs_sreq_trace_submit);
 			slice = netfs_prepare_read_iterator(subreq);
+			if (slice < 0)
+				goto prep_iter_failed;
 			netfs_read_cache_to_pagecache(rreq, subreq);
 			goto done;
 		}
@@ -318,6 +314,14 @@ static void netfs_read_to_pagecache(struct netfs_io_request *rreq)
 		WARN_ON_ONCE(1);
 		break;
 
+	prep_iter_failed:
+		ret = slice;
+	prep_failed:
+		subreq->error = ret;
+		atomic_dec(&rreq->nr_outstanding);
+		netfs_put_subrequest(subreq, false, netfs_sreq_trace_put_cancel);
+		break;
+
 	done:
 		size -= slice;
 		start += slice;