[PATCH RESEND] fs/netfs/read_collect: add to next->prev_donated

[PATCH RESEND] fs/netfs/read_collect: add to next->prev_donated

[Max Kellermann]

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 <max.kellermann@ionos.com>
Signed-off-by: David Howells <dhowells@redhat.com>
---
 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

Re: [PATCH RESEND] fs/netfs/read_collect: add to next->prev_donated

[Salvatore Bonaccorso]

Hi,

On Thu, Feb 20, 2025 at 04:24:50PM +0100, Max Kellermann wrote:
> 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 <max.kellermann@ionos.com>
> Signed-off-by: David Howells <dhowells@redhat.com>
> ---
>  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

Unless I did some mistakes researching both the stable, netfs lists,
did this felt through the cracks and is still missing for to be picked
for the 6.12.y and 6.13.y series?

Regards,
Salvatore

Re: [PATCH RESEND] fs/netfs/read_collect: add to next->prev_donated

[David Howells]

Hi Greg,

Could you pick this up for 6.12.y and 6.13.y?

https://lore.kernel.org/netfs/20250220152450.1075727-1-max.kellermann@ionos.com/

Thanks,
David

Re: [PATCH RESEND] fs/netfs/read_collect: add to next->prev_donated

[Greg Kroah-Hartman]

On Mon, Mar 17, 2025 at 10:03:12AM +0000, David Howells wrote:
> Hi Greg,
> 
> Could you pick this up for 6.12.y and 6.13.y?
> 
> https://lore.kernel.org/netfs/20250220152450.1075727-1-max.kellermann@ionos.com/

Oops, missed this, sorry, now queued up.

greg k-h

Patch "fs/netfs/read_collect: add to next->prev_donated" has been added to the 6.12-stable tree

[gregkh]

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

    fs/netfs/read_collect: add to next->prev_donated

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:
     fs-netfs-read_collect-add-to-next-prev_donated.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@vger.kernel.org> know about it.


From stable+bounces-118455-greg=kroah.com@vger.kernel.org Thu Feb 20 07:27:34 2025
From: Max Kellermann <max.kellermann@ionos.com>
Date: Thu, 20 Feb 2025 16:24:50 +0100
Subject: fs/netfs/read_collect: add to next->prev_donated
To: dhowells@redhat.com, netfs@lists.linux.dev, linux-kernel@vger.kernel.org
Cc: Max Kellermann <max.kellermann@ionos.com>, stable@vger.kernel.org
Message-ID: <20250220152450.1075727-1-max.kellermann@ionos.com>

From: Max Kellermann <max.kellermann@ionos.com>

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 <max.kellermann@ionos.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 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



Patches currently in stable-queue which might be from max.kellermann@ionos.com are

queue-6.12/fs-netfs-read_collect-add-to-next-prev_donated.patch

Patch "fs/netfs/read_collect: add to next->prev_donated" has been added to the 6.13-stable tree

[gregkh]

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

    fs/netfs/read_collect: add to next->prev_donated

to the 6.13-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:
     fs-netfs-read_collect-add-to-next-prev_donated.patch
and it can be found in the queue-6.13 subdirectory.

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


From stable+bounces-118455-greg=kroah.com@vger.kernel.org Thu Feb 20 07:27:34 2025
From: Max Kellermann <max.kellermann@ionos.com>
Date: Thu, 20 Feb 2025 16:24:50 +0100
Subject: fs/netfs/read_collect: add to next->prev_donated
To: dhowells@redhat.com, netfs@lists.linux.dev, linux-kernel@vger.kernel.org
Cc: Max Kellermann <max.kellermann@ionos.com>, stable@vger.kernel.org
Message-ID: <20250220152450.1075727-1-max.kellermann@ionos.com>

From: Max Kellermann <max.kellermann@ionos.com>

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 <max.kellermann@ionos.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/netfs/read_collect.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- 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);
 	}


Patches currently in stable-queue which might be from max.kellermann@ionos.com are

queue-6.13/fs-netfs-read_collect-add-to-next-prev_donated.patch