[PATCH net v4] net: mvneta: clear XDP pfmemalloc flag between frames

[PATCH net v4] net: mvneta: clear XDP pfmemalloc flag between frames

[Lorenzo Bianconi]

mvneta_swbm_add_rx_fragment() sets XDP_FLAGS_FRAGS_PF_MEMALLOC on the
xdp_buff when a fragment page is a pfmemalloc one (page under memory
pressure). The xdp_buff is reused for the next frame, but only the
XDP_FLAGS_HAS_FRAGS bit was cleared at frame start, so the pfmemalloc
bit leaked from one frame into the following ones. mvneta_swbm_build_skb()
propagates the flag to skb->pfmemalloc through xdp_update_skb_frags_info(),
so the skb of a subsequent fragmented frame could be wrongly marked as
pfmemalloc even if none of its pages are under pressure.

Clear all the xdp_buff flags in mvneta_swbm_rx_frame(), which is invoked
for each new frame, instead of just the XDP_FLAGS_HAS_FRAGS bit.

Fixes: ed7a58cb40bd ("net: marvell: rely on xdp_update_skb_shared_info utility routine")
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@oss.qualcomm.com>
---
Changes in v4:
- Rename xdp_reinit_buf() in xdp_reinit_buff().
- Link to v3: https://lore.kernel.org/r/20260928-mvneta-xdp-clear-frag-fix-v3-1-af4a51499eaf@oss.qualcomm.com

Changes in v3:
- Rename xdp_buff_clear_flags() in xdp_reinit_buf().
- Link to v2: https://lore.kernel.org/r/20260923-mvneta-xdp-clear-frag-fix-v2-1-298693a7ea6b@oss.qualcomm.com

Changes in v2:
- Introduce xdp_buff_clear_flags() utility routine.
- Link to v1: https://lore.kernel.org/r/20260920-mvneta-xdp-clear-frag-fix-v1-1-d7efadecf959@oss.qualcomm.com
---
 drivers/net/ethernet/marvell/mvneta.c | 2 +-
 include/net/xdp.h                     | 5 +++++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
index 543e566425c1..4f479b6f731e 100644
--- a/drivers/net/ethernet/marvell/mvneta.c
+++ b/drivers/net/ethernet/marvell/mvneta.c
@@ -2340,7 +2340,7 @@ mvneta_swbm_rx_frame(struct mvneta_port *pp,
 
 	/* Prefetch header */
 	prefetch(data);
-	xdp_buff_clear_frags_flag(xdp);
+	xdp_reinit_buff(xdp);
 	xdp_prepare_buff(xdp, data, pp->rx_offset_correction + MVNETA_MH_SIZE,
 			 data_len, true);
 }
diff --git a/include/net/xdp.h b/include/net/xdp.h
index aa742f413c35..07231adfb5f8 100644
--- a/include/net/xdp.h
+++ b/include/net/xdp.h
@@ -106,6 +106,11 @@ struct xdp_buff {
 	};
 };
 
+static __always_inline void xdp_reinit_buff(struct xdp_buff *xdp)
+{
+	xdp->flags = 0;
+}
+
 static __always_inline bool xdp_buff_has_frags(const struct xdp_buff *xdp)
 {
 	return !!(xdp->flags & XDP_FLAGS_HAS_FRAGS);

---
base-commit: 54518e0e827f4ca9229ae657022c60bf60f5c1bf
change-id: 20260919-mvneta-xdp-clear-frag-fix-7ac691e1659b

Best regards,
-- 
Lorenzo Bianconi <lorenzo.bianconi@oss.qualcomm.com>

Re: [PATCH net v4] net: mvneta: clear XDP pfmemalloc flag between frames

[netdev-bot+sinfo]

Hi!

This is an automated message. This series looks like a fix, but its
commit messages seem to be missing some information:

 - How the issue was discovered, e.g. hit in production, hit during
   development, syzbot report, manual code inspection, LLM or static
   analysis tool scan.

 - Whether the issue was actually triggered, or is only theoretical
   (e.g. found by code inspection). If it was triggered please include
   the symptoms, like the stack trace or error messages.

 - What hardware the change was tested on. For driver fixes please
   mention the device (and if relevant firmware version) used for
   testing, or say that the change was not tested on real hardware.

Please do not repost the series just to address the above. Instead,
reply to this email with the missing information, so that reviewers
can take it into account. If the series needs another revision for
other reasons, please include the information in the commit messages
then.

The evaluation is done by an LLM so it may be wrong, if you think
that is the case please reply and explain.

Re: [PATCH net v4] net: mvneta: clear XDP pfmemalloc flag between frames

[Toke Høiland-Jørgensen]

Lorenzo Bianconi <lorenzo.bianconi@oss.qualcomm.com> writes:

> mvneta_swbm_add_rx_fragment() sets XDP_FLAGS_FRAGS_PF_MEMALLOC on the
> xdp_buff when a fragment page is a pfmemalloc one (page under memory
> pressure). The xdp_buff is reused for the next frame, but only the
> XDP_FLAGS_HAS_FRAGS bit was cleared at frame start, so the pfmemalloc
> bit leaked from one frame into the following ones. mvneta_swbm_build_skb()
> propagates the flag to skb->pfmemalloc through xdp_update_skb_frags_info(),
> so the skb of a subsequent fragmented frame could be wrongly marked as
> pfmemalloc even if none of its pages are under pressure.
>
> Clear all the xdp_buff flags in mvneta_swbm_rx_frame(), which is invoked
> for each new frame, instead of just the XDP_FLAGS_HAS_FRAGS bit.
>
> Fixes: ed7a58cb40bd ("net: marvell: rely on xdp_update_skb_shared_info utility routine")
> Reviewed-by: Simon Horman <horms@kernel.org>
> Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@oss.qualcomm.com>

Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>

Re: [PATCH net v4] net: mvneta: clear XDP pfmemalloc flag between frames

[Jakub Kicinski]

On Tue, 29 Sep 2026 15:43:03 +0200 Lorenzo Bianconi wrote:
> mvneta_swbm_add_rx_fragment() sets XDP_FLAGS_FRAGS_PF_MEMALLOC on the
> xdp_buff when a fragment page is a pfmemalloc one (page under memory
> pressure). The xdp_buff is reused for the next frame, but only the
> XDP_FLAGS_HAS_FRAGS bit was cleared at frame start, so the pfmemalloc
> bit leaked from one frame into the following ones. mvneta_swbm_build_skb()
> propagates the flag to skb->pfmemalloc through xdp_update_skb_frags_info(),
> so the skb of a subsequent fragmented frame could be wrongly marked as
> pfmemalloc even if none of its pages are under pressure.
> 
> Clear all the xdp_buff flags in mvneta_swbm_rx_frame(), which is invoked
> for each new frame, instead of just the XDP_FLAGS_HAS_FRAGS bit.

Is there a reason you're not adding the info sinfo bot is asking for?

Re: [PATCH net v4] net: mvneta: clear XDP pfmemalloc flag between frames

[Lorenzo Bianconi]

[-- Attachment #1: Type: text/plain, Size: 977 bytes --]

> On Tue, 29 Sep 2026 15:43:03 +0200 Lorenzo Bianconi wrote:
> > mvneta_swbm_add_rx_fragment() sets XDP_FLAGS_FRAGS_PF_MEMALLOC on the
> > xdp_buff when a fragment page is a pfmemalloc one (page under memory
> > pressure). The xdp_buff is reused for the next frame, but only the
> > XDP_FLAGS_HAS_FRAGS bit was cleared at frame start, so the pfmemalloc
> > bit leaked from one frame into the following ones. mvneta_swbm_build_skb()
> > propagates the flag to skb->pfmemalloc through xdp_update_skb_frags_info(),
> > so the skb of a subsequent fragmented frame could be wrongly marked as
> > pfmemalloc even if none of its pages are under pressure.
> > 
> > Clear all the xdp_buff flags in mvneta_swbm_rx_frame(), which is invoked
> > for each new frame, instead of just the XDP_FLAGS_HAS_FRAGS bit.
> 
> Is there a reason you're not adding the info sinfo bot is asking for?

nope sorry :(. I have just forgot to reply. I will do next time.

Regards,
Lorenzo

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 228 bytes --]

Re: [PATCH net v4] net: mvneta: clear XDP pfmemalloc flag between frames

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Tue, 29 Sep 2026 15:43:03 +0200 you wrote:
> mvneta_swbm_add_rx_fragment() sets XDP_FLAGS_FRAGS_PF_MEMALLOC on the
> xdp_buff when a fragment page is a pfmemalloc one (page under memory
> pressure). The xdp_buff is reused for the next frame, but only the
> XDP_FLAGS_HAS_FRAGS bit was cleared at frame start, so the pfmemalloc
> bit leaked from one frame into the following ones. mvneta_swbm_build_skb()
> propagates the flag to skb->pfmemalloc through xdp_update_skb_frags_info(),
> so the skb of a subsequent fragmented frame could be wrongly marked as
> pfmemalloc even if none of its pages are under pressure.
> 
> [...]

Here is the summary with links:
  - [net,v4] net: mvneta: clear XDP pfmemalloc flag between frames
    https://git.kernel.org/netdev/net/c/8f1c2a10500a

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html