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[2003:dc:6f00:7700:230:64ff:fe74:809]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-abb9f3a695dsm751274266b.2.2025.02.20.07.24.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 20 Feb 2025 07:24:54 -0800 (PST) From: Max Kellermann To: dhowells@redhat.com, netfs@lists.linux.dev, linux-kernel@vger.kernel.org Cc: Max Kellermann , stable@vger.kernel.org Subject: [PATCH RESEND] fs/netfs/read_collect: add to next->prev_donated Date: Thu, 20 Feb 2025 16:24:50 +0100 Message-ID: <20250220152450.1075727-1-max.kellermann@ionos.com> X-Mailer: git-send-email 2.47.2 Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 --- 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 8878b46589ff..cafadfe8e858 100644 --- a/fs/netfs/read_collect.c +++ b/fs/netfs/read_collect.c @@ -284,7 +284,7 @@ static bool netfs_consume_read_data(struct netfs_io_subrequest *subreq, bool was 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); } -- 2.47.2