From f491405377615ad571501e600950ac0fc4b569da Mon Sep 17 00:00:00 2001 From: Max Kellermann Date: Thu, 20 Feb 2025 16:24:50 +0100 Subject: [PATCH] fs/netfs/read_collect: add to next->prev_donated origin: https://lore.kernel.org/netfs/20250220152450.1075727-1-max.kellermann@ionos.com/ Bug-Debian: https://bugs.debian.org/1099591 Bug-Debian: https://bugs.debian.org/1098698 If multiple subrequests donate data to the same "next" request (depending on the subrequest completion order), each of them would overwrite the `prev_donated` field, causing data corruption and a BUG() crash ("Can't donate prior to front"). Fixes: ee4cdf7ba857 ("netfs: Speed up buffered reading") Closes: https://lore.kernel.org/netfs/CAKPOu+_4mUwYgQtRTbXCmi+-k3PGvLysnPadkmHOyB7Gz0iSMA@mail.gmail.com/ Cc: stable@vger.kernel.org Signed-off-by: Max Kellermann Signed-off-by: David Howells Gbp-Pq: Topic bugfix/all Gbp-Pq: Name fs-netfs-read_collect-add-to-next-prev_donated.patch --- fs/netfs/read_collect.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/netfs/read_collect.c b/fs/netfs/read_collect.c index 3b9461f5e71..eae415efae2 100644 --- a/fs/netfs/read_collect.c +++ b/fs/netfs/read_collect.c @@ -284,7 +284,7 @@ donation_changed: netfs_trace_donate_to_deferred_next); } else { next = list_next_entry(subreq, rreq_link); - WRITE_ONCE(next->prev_donated, excess); + WRITE_ONCE(next->prev_donated, next->prev_donated + excess); trace_netfs_donate(rreq, subreq, next, excess, netfs_trace_donate_to_next); } -- 2.30.2