linux-stable.git/net/xdp, branch linux-rolling-lts Linux kernel stable tree xsk: validate metadata when processing requests 2026-08-19T16:17:28+00:00 Stanislav Fomichev sdf.kernel@gmail.com 2026-07-27T16:19:59+00:00 5fd121971912dee2f5af1efec64462ac722deb17 [ Upstream commit 849b1664dbda1cf6c63e0fd4f9dec23782b8c851 ] The zero-copy path validates TX metadata while obtaining the descriptor context, then reads it again later when preparing the hardware request. User space can change the metadata between those operations and bypass the original validation. Validate the metadata in xsk_tx_metadata_request() and use the resulting flags snapshot for every feature check. Read request fields once so all zero-copy drivers process only values observed after successful validation. Fixes: ca4419f15abd ("xsk: Add launch time hardware offload support to XDP Tx metadata") Cc: Cen Zhang (Microsoft) <blbllhy@gmail.com> Signed-off-by: Stanislav Fomichev <sdf@fomichev.me> Link: https://patch.msgid.link/20260727161959.885642-7-sdf@fomichev.me Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 849b1664dbda1cf6c63e0fd4f9dec23782b8c851 ]

The zero-copy path validates TX metadata while obtaining the descriptor
context, then reads it again later when preparing the hardware request.
User space can change the metadata between those operations and bypass the
original validation.

Validate the metadata in xsk_tx_metadata_request() and use the resulting
flags snapshot for every feature check. Read request fields once so all
zero-copy drivers process only values observed after successful
validation.

Fixes: ca4419f15abd ("xsk: Add launch time hardware offload support to XDP Tx metadata")
Cc: Cen Zhang (Microsoft) <blbllhy@gmail.com>
Signed-off-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://patch.msgid.link/20260727161959.885642-7-sdf@fomichev.me
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
xsk: validate launch-time metadata size 2026-08-19T16:17:27+00:00 Stanislav Fomichev sdf.kernel@gmail.com 2026-07-27T16:19:57+00:00 af511afa1d2977f384044df78d6fbf9fba653f7a [ Upstream commit 439ce2dddf3d22129b9113a7881637256a35e936 ] Launch-time metadata extends beyond the first 16 bytes of struct xsk_tx_metadata. Reject the request when the registered metadata area does not contain the complete field. Snapshot the validated flags for the generic transmit path and use that snapshot for request and completion processing, avoiding inconsistent decisions if user space changes the flags concurrently. Note that only xsk_skb_metadata is properly using the flags, __xsk_buff_get_metadata ignores them. Next commits address that. Fixes: ca4419f15abd ("xsk: Add launch time hardware offload support to XDP Tx metadata") Cc: Cen Zhang (Microsoft) <blbllhy@gmail.com> Signed-off-by: Stanislav Fomichev <sdf@fomichev.me> Link: https://patch.msgid.link/20260727161959.885642-5-sdf@fomichev.me Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 439ce2dddf3d22129b9113a7881637256a35e936 ]

Launch-time metadata extends beyond the first 16 bytes of struct
xsk_tx_metadata. Reject the request when the registered metadata area does
not contain the complete field.

Snapshot the validated flags for the generic transmit path and use that
snapshot for request and completion processing, avoiding inconsistent
decisions if user space changes the flags concurrently.

Note that only xsk_skb_metadata is properly using the flags,
__xsk_buff_get_metadata ignores them. Next commits address that.

Fixes: ca4419f15abd ("xsk: Add launch time hardware offload support to XDP Tx metadata")
Cc: Cen Zhang (Microsoft) <blbllhy@gmail.com>
Signed-off-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://patch.msgid.link/20260727161959.885642-5-sdf@fomichev.me
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
xsk: clear metadata pointer when no timestamp is requested 2026-08-19T16:17:26+00:00 Stanislav Fomichev sdf.kernel@gmail.com 2026-07-27T16:19:56+00:00 0ba2e1eb07a826d021344e2f146b6716c58139eb [ Upstream commit 9f60a67df8d3c862503bee62bada8e7089cba438 ] User space can change metadata flags after request processing. Rereading them during completion can therefore make the kernel write a timestamp that was not requested when the packet was submitted. Clear the metadata pointer during request processing unless timestamp completion is requested. Completion handling can then use the pointer itself instead of rereading the flags. On the mlx5 multi-packet WQE path metadata is evaluated per batch: xsk_tx_metadata_request() runs only for the descriptor that starts a session, just like the checksum offload that is applied once through the shared WQE. Only that descriptor's pointer is reset, so completion handling can record a timestamp for the other descriptors of the session regardless of their own XDP_TXMD_FLAGS_TIMESTAMP bit. The write stays inside the metadata area; the single-WQE, other zero-copy, and generic paths reset the pointer per descriptor and are unaffected. Fixes: ca4419f15abd ("xsk: Add launch time hardware offload support to XDP Tx metadata") Cc: Cen Zhang (Microsoft) <blbllhy@gmail.com> Signed-off-by: Stanislav Fomichev <sdf@fomichev.me> Link: https://patch.msgid.link/20260727161959.885642-4-sdf@fomichev.me Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 9f60a67df8d3c862503bee62bada8e7089cba438 ]

User space can change metadata flags after request processing. Rereading
them during completion can therefore make the kernel write a timestamp
that was not requested when the packet was submitted.

Clear the metadata pointer during request processing unless timestamp
completion is requested. Completion handling can then use the pointer
itself instead of rereading the flags.

On the mlx5 multi-packet WQE path metadata is evaluated per batch:
xsk_tx_metadata_request() runs only for the descriptor that starts a
session, just like the checksum offload that is applied once through the
shared WQE. Only that descriptor's pointer is reset, so completion
handling can record a timestamp for the other descriptors of the session
regardless of their own XDP_TXMD_FLAGS_TIMESTAMP bit. The write stays
inside the metadata area; the single-WQE, other zero-copy, and generic
paths reset the pointer per descriptor and are unaffected.

Fixes: ca4419f15abd ("xsk: Add launch time hardware offload support to XDP Tx metadata")
Cc: Cen Zhang (Microsoft) <blbllhy@gmail.com>
Signed-off-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://patch.msgid.link/20260727161959.885642-4-sdf@fomichev.me
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
xsk: require at least 16 bytes of TX metadata 2026-08-19T16:17:26+00:00 Stanislav Fomichev sdf.kernel@gmail.com 2026-07-27T16:19:54+00:00 642c6e73fce17fdca93a5793c4d22359fda866d7 [ Upstream commit 1bb30b181d9f0484e141f8411e15ed906d5c6780 ] AF_XDP accepts a TX metadata length as small as eight bytes, but every supported request needs the flags plus at least one eight-byte request field. Such short metadata also lets the kernel read beyond the registered area. Require 16 bytes rather than sizeof(struct xsk_tx_metadata) to preserve compatibility with applications that do not use launch-time metadata. Fixes: 341ac980eab9 ("xsk: Support tx_metadata_len") Reported-by: AutonomousCodeSecurity@microsoft.com Reported-by: Cen Zhang (Microsoft) <blbllhy@gmail.com> Link: https://lore.kernel.org/netdev/20260720155210.34229-1-blbllhy@gmail.com/ Signed-off-by: Stanislav Fomichev <sdf@fomichev.me> Link: https://patch.msgid.link/20260727161959.885642-2-sdf@fomichev.me Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 1bb30b181d9f0484e141f8411e15ed906d5c6780 ]

AF_XDP accepts a TX metadata length as small as eight bytes, but every
supported request needs the flags plus at least one eight-byte request
field. Such short metadata also lets the kernel read beyond the registered
area.

Require 16 bytes rather than sizeof(struct xsk_tx_metadata) to preserve
compatibility with applications that do not use launch-time metadata.

Fixes: 341ac980eab9 ("xsk: Support tx_metadata_len")
Reported-by: AutonomousCodeSecurity@microsoft.com
Reported-by: Cen Zhang (Microsoft) <blbllhy@gmail.com>
Link: https://lore.kernel.org/netdev/20260720155210.34229-1-blbllhy@gmail.com/
Signed-off-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://patch.msgid.link/20260727161959.885642-2-sdf@fomichev.me
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
xsk: drain continuation descs after overflow in xsk_build_skb() 2026-08-09T18:25:02+00:00 Jason Xing kernelxing@tencent.com 2026-07-19T13:56:05+00:00 ceb00cb87a22c42d20c39336213db2b843ca9e34 [ Upstream commit bd44a6dcd4248883de90f5dad53ae80066e27096 ] Fix generic xmit path multi-buffer logic when packets are either too big (count of descriptors exceed MAX_SKB_FRAGS) or an invalid descriptor is included in fragmented packet. Introduce xdp_sock::drain_cont and act upon this flag - when it is set, keep on consuming descriptors from AF_XDP Tx ring and put them directly onto Cq. Previously these descriptors were silently lost and could never be reached again. Fixes: cf24f5a5feea ("xsk: add support for AF_XDP multi-buffer on Tx path") Closes: https://lore.kernel.org/all/20260425041726.85FB3C2BCB2@smtp.kernel.org/ Reviewed-by: Jason Xing <kernelxing@tencent.com> Co-developed-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com> # wrapped cq addr submission onto routine Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com> Signed-off-by: Jason Xing <kernelxing@tencent.com> Acked-by: Stanislav Fomichev <sdf@fomichev.me> Link: https://patch.msgid.link/20260719135609.147823-3-maciej.fijalkowski@intel.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit bd44a6dcd4248883de90f5dad53ae80066e27096 ]

Fix generic xmit path multi-buffer logic when packets are either too big
(count of descriptors exceed MAX_SKB_FRAGS) or an invalid descriptor is
included in fragmented packet. Introduce xdp_sock::drain_cont and act
upon this flag - when it is set, keep on consuming descriptors from
AF_XDP Tx ring and put them directly onto Cq. Previously these
descriptors were silently lost and could never be reached again.

Fixes: cf24f5a5feea ("xsk: add support for AF_XDP multi-buffer on Tx path")
Closes: https://lore.kernel.org/all/20260425041726.85FB3C2BCB2@smtp.kernel.org/
Reviewed-by: Jason Xing <kernelxing@tencent.com>
Co-developed-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com> # wrapped cq addr submission onto routine
Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Signed-off-by: Jason Xing <kernelxing@tencent.com>
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://patch.msgid.link/20260719135609.147823-3-maciej.fijalkowski@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
xsk: use a smaller new lock for shared pool case 2026-08-09T18:25:02+00:00 Jason Xing kernelxing@tencent.com 2025-10-30T00:06:46+00:00 411554cb868b879268e377c96bab3802d63e0b97 [ Upstream commit 30ed05adca4a05c50594384cff18910858dd1d35 ] - Split cq_lock into two smaller locks: cq_prod_lock and cq_cached_prod_lock - Avoid disabling/enabling interrupts in the hot xmit path In either xsk_cq_cancel_locked() or xsk_cq_reserve_locked() function, the race condition is only between multiple xsks sharing the same pool. They are all in the process context rather than interrupt context, so now the small lock named cq_cached_prod_lock can be used without handling interrupts. While cq_cached_prod_lock ensures the exclusive modification of @cached_prod, cq_prod_lock in xsk_cq_submit_addr_locked() only cares about @producer and corresponding @desc. Both of them don't necessarily be consistent with @cached_prod protected by cq_cached_prod_lock. That's the reason why the previous big lock can be split into two smaller ones. Please note that SPSC rule is all about the global state of producer and consumer that can affect both layers instead of local or cached ones. Frequently disabling and enabling interrupt are very time consuming in some cases, especially in a per-descriptor granularity, which now can be avoided after this optimization, even when the pool is shared by multiple xsks. With this patch, the performance number[1] could go from 1,872,565 pps to 1,961,009 pps. It's a minor rise of around 5%. [1]: taskset -c 1 ./xdpsock -i enp2s0f1 -q 0 -t -S -s 64 Signed-off-by: Jason Xing <kernelxing@tencent.com> Acked-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com> Link: https://patch.msgid.link/20251030000646.18859-3-kerneljasonxing@gmail.com Signed-off-by: Paolo Abeni <pabeni@redhat.com> Stable-dep-of: bd44a6dcd424 ("xsk: drain continuation descs after overflow in xsk_build_skb()") Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 30ed05adca4a05c50594384cff18910858dd1d35 ]

- Split cq_lock into two smaller locks: cq_prod_lock and
  cq_cached_prod_lock
- Avoid disabling/enabling interrupts in the hot xmit path

In either xsk_cq_cancel_locked() or xsk_cq_reserve_locked() function,
the race condition is only between multiple xsks sharing the same
pool. They are all in the process context rather than interrupt context,
so now the small lock named cq_cached_prod_lock can be used without
handling interrupts.

While cq_cached_prod_lock ensures the exclusive modification of
@cached_prod, cq_prod_lock in xsk_cq_submit_addr_locked() only cares
about @producer and corresponding @desc. Both of them don't necessarily
be consistent with @cached_prod protected by cq_cached_prod_lock.
That's the reason why the previous big lock can be split into two
smaller ones. Please note that SPSC rule is all about the global state
of producer and consumer that can affect both layers instead of local
or cached ones.

Frequently disabling and enabling interrupt are very time consuming
in some cases, especially in a per-descriptor granularity, which now
can be avoided after this optimization, even when the pool is shared by
multiple xsks.

With this patch, the performance number[1] could go from 1,872,565 pps
to 1,961,009 pps. It's a minor rise of around 5%.

[1]: taskset -c 1 ./xdpsock -i enp2s0f1 -q 0 -t -S -s 64

Signed-off-by: Jason Xing <kernelxing@tencent.com>
Acked-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Link: https://patch.msgid.link/20251030000646.18859-3-kerneljasonxing@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Stable-dep-of: bd44a6dcd424 ("xsk: drain continuation descs after overflow in xsk_build_skb()")
Signed-off-by: Sasha Levin <sashal@kernel.org>
xsk: fix buffer leak in xsk_drop_skb() for AF_XDP multi-buffer Tx 2026-08-09T18:25:02+00:00 Jason Xing kernelxing@tencent.com 2026-07-19T13:56:04+00:00 05e283466b86e0b25a5209a3eafe87aa9886064a [ Upstream commit a3c8382ebce4780c6b3ace2c09bc342313ac0186 ] This patch is inspired by the check[1] from sashiko. It says when overflow happens, the address of cq to be published is invalid. Actually the severer thing is the whole process of publishing the address of cq in this particular case is not right: it should truely publish the address and advance the cached_prod in cq as long as it reads descriptors from txq. The following is the full analysis. xsk_drop_skb() is called in three places, which all discard a partially built multi-buffer skb: 1) xsk_build_skb() -EOVERFLOW error path: packet exceeds MAX_SKB_FRAGS 2) __xsk_generic_xmit() post-loop cleanup: an invalid descriptor in the TX ring prevents the partial packet from completing 3) xsk_release(): socket close while xs->skb holds an incomplete packet In all three cases, the TX descriptors for the already-processed frags have been consumed from the TX ring (xskq_cons_release), and CQ slots have been reserved. However, xsk_drop_skb() calls xsk_consume_skb() which cancels the CQ reservations via xsk_cq_cancel_locked(). Since the buffer addresses never appear in the completion queue, userspace permanently loses track of these buffers. Fix this by letting consume_skb() trigger the existing xsk_destruct_skb destructor, which already submits buffer addresses to the CQ via xsk_cq_submit_addr_locked(). Note that cancelling the descriptors back to the TX ring (via xskq_cons_cancel_n) is not a appropriate option because an oversized packet that always exceeds MAX_SKB_FRAGS would be retried indefinitely, which is an obviously deadlock bug in the TX path. Also move the desc->addr assignment in xsk_build_skb() above the overflow check so that the current descriptor's address is recorded before a potential -EOVERFLOW jump to free_err, consistent with the zerocopy path in xsk_build_skb_zerocopy(). [1]: https://lore.kernel.org/all/20260425041726.85FB3C2BCB2@smtp.kernel.org/ Fixes: cf24f5a5feea ("xsk: add support for AF_XDP multi-buffer on Tx path") Acked-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com> Signed-off-by: Jason Xing <kernelxing@tencent.com> Acked-by: Stanislav Fomichev <sdf@fomichev.me> Link: https://patch.msgid.link/20260719135609.147823-2-maciej.fijalkowski@intel.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit a3c8382ebce4780c6b3ace2c09bc342313ac0186 ]

This patch is inspired by the check[1] from sashiko. It says when
overflow happens, the address of cq to be published is invalid.
Actually the severer thing is the whole process of publishing the
address of cq in this particular case is not right: it should truely
publish the address and advance the cached_prod in cq as long as it
reads descriptors from txq.

The following is the full analysis.
xsk_drop_skb() is called in three places, which all discard a partially
built multi-buffer skb:
1) xsk_build_skb() -EOVERFLOW error path: packet exceeds MAX_SKB_FRAGS
2) __xsk_generic_xmit() post-loop cleanup: an invalid descriptor in
   the TX ring prevents the partial packet from completing
3) xsk_release(): socket close while xs->skb holds an incomplete packet

In all three cases, the TX descriptors for the already-processed frags
have been consumed from the TX ring (xskq_cons_release), and CQ slots
have been reserved. However, xsk_drop_skb() calls xsk_consume_skb()
which cancels the CQ reservations via xsk_cq_cancel_locked(). Since
the buffer addresses never appear in the completion queue, userspace
permanently loses track of these buffers.

Fix this by letting consume_skb() trigger the existing xsk_destruct_skb
destructor, which already submits buffer addresses to the CQ via
xsk_cq_submit_addr_locked().

Note that cancelling the descriptors back to the TX ring (via
xskq_cons_cancel_n) is not a appropriate option because an oversized
packet that always exceeds MAX_SKB_FRAGS would be retried indefinitely,
which is an obviously deadlock bug in the TX path.

Also move the desc->addr assignment in xsk_build_skb() above the
overflow check so that the current descriptor's address is recorded
before a potential -EOVERFLOW jump to free_err, consistent with the
zerocopy path in xsk_build_skb_zerocopy().

[1]: https://lore.kernel.org/all/20260425041726.85FB3C2BCB2@smtp.kernel.org/

Fixes: cf24f5a5feea ("xsk: add support for AF_XDP multi-buffer on Tx path")
Acked-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Signed-off-by: Jason Xing <kernelxing@tencent.com>
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://patch.msgid.link/20260719135609.147823-2-maciej.fijalkowski@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
xsk: cache csum_start/csum_offset to fix TOCTOU in xsk_skb_metadata() 2026-06-19T11:43:54+00:00 Jason Xing kernelxing@tencent.com 2026-05-30T04:26:30+00:00 0dfe05b938435892875e07771170051346412df9 [ Upstream commit 22ba97ea9cc1f63a0d0244fae38057ed452b6ac7 ] The TX metadata area resides in the UMEM buffer which is memory-mapped and concurrently writable by userspace. In xsk_skb_metadata(), csum_start and csum_offset are read from shared memory for bounds validation, then read again for skb assignment. A malicious userspace application can race to overwrite these values between the two reads, bypassing the bounds check and causing out-of-bounds memory access during checksum computation in the transmit path. Fix this by reading csum_start and csum_offset into local variables once, then using the local copies for both validation and assignment. Note that other metadata fields (flags, launch_time) and the cached csum fields may be mutually inconsistent due to concurrent userspace writes, but this is benign: the only security-critical invariant is that each field's validated value is the same one used, which local caching guarantees. Closes: https://lore.kernel.org/all/20260503200927.73EA1C2BCB4@smtp.kernel.org/ Reviewed-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com> Signed-off-by: Jason Xing <kernelxing@tencent.com> Acked-by: Stanislav Fomichev <sdf@fomichev.me> Fixes: 48eb03dd2630 ("xsk: Add TX timestamp and TX checksum offload support") Link: https://patch.msgid.link/20260530042630.80626-1-kerneljasonxing@gmail.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 22ba97ea9cc1f63a0d0244fae38057ed452b6ac7 ]

The TX metadata area resides in the UMEM buffer which is memory-mapped
and concurrently writable by userspace. In xsk_skb_metadata(),
csum_start and csum_offset are read from shared memory for bounds
validation, then read again for skb assignment. A malicious userspace
application can race to overwrite these values between the two reads,
bypassing the bounds check and causing out-of-bounds memory access
during checksum computation in the transmit path.

Fix this by reading csum_start and csum_offset into local variables
once, then using the local copies for both validation and assignment.

Note that other metadata fields (flags, launch_time) and the cached
csum fields may be mutually inconsistent due to concurrent userspace
writes, but this is benign: the only security-critical invariant is
that each field's validated value is the same one used, which local
caching guarantees.

Closes: https://lore.kernel.org/all/20260503200927.73EA1C2BCB4@smtp.kernel.org/
Reviewed-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Signed-off-by: Jason Xing <kernelxing@tencent.com>
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Fixes: 48eb03dd2630 ("xsk: Add TX timestamp and TX checksum offload support")
Link: https://patch.msgid.link/20260530042630.80626-1-kerneljasonxing@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
xsk: validate MTU against usable frame size on bind 2026-04-22T11:22:21+00:00 Maciej Fijalkowski maciej.fijalkowski@intel.com 2026-04-02T15:49:54+00:00 25e1e91a8da819924df0b16e3812d7b24c8ce133 [ Upstream commit 36ee60b569ba0dfb6f961333b90d19ab5b323fa9 ] AF_XDP bind currently accepts zero-copy pool configurations without verifying that the device MTU fits into the usable frame space provided by the UMEM chunk. This becomes a problem since we started to respect tailroom which is subtracted from chunk_size (among with headroom). 2k chunk size might not provide enough space for standard 1500 MTU, so let us catch such settings at bind time. Furthermore, validate whether underlying HW will be able to satisfy configured MTU wrt XSK's frame size multiplied by supported Rx buffer chain length (that is exposed via net_device::xdp_zc_max_segs). Fixes: 24ea50127ecf ("xsk: support mbuf on ZC RX") Reviewed-by: Björn Töpel <bjorn@kernel.org> Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com> Link: https://patch.msgid.link/20260402154958.562179-5-maciej.fijalkowski@intel.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 36ee60b569ba0dfb6f961333b90d19ab5b323fa9 ]

AF_XDP bind currently accepts zero-copy pool configurations without
verifying that the device MTU fits into the usable frame space provided
by the UMEM chunk.

This becomes a problem since we started to respect tailroom which is
subtracted from chunk_size (among with headroom). 2k chunk size might
not provide enough space for standard 1500 MTU, so let us catch such
settings at bind time. Furthermore, validate whether underlying HW will
be able to satisfy configured MTU wrt XSK's frame size multiplied by
supported Rx buffer chain length (that is exposed via
net_device::xdp_zc_max_segs).

Fixes: 24ea50127ecf ("xsk: support mbuf on ZC RX")
Reviewed-by: Björn Töpel <bjorn@kernel.org>
Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Link: https://patch.msgid.link/20260402154958.562179-5-maciej.fijalkowski@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
xsk: fix XDP_UMEM_SG_FLAG issues 2026-04-22T11:22:21+00:00 Maciej Fijalkowski maciej.fijalkowski@intel.com 2026-04-02T15:49:53+00:00 4947e2ae9c5737d9cdfbe5d32006b4a62435d67e [ Upstream commit 93e84fe45b752d17a5a46b306ed78f0133bbc719 ] Currently xp_assign_dev_shared() is missing XDP_USE_SG being propagated to flags so set it in order to preserve mtu check that is supposed to be done only when no multi-buffer setup is in picture. Also, this flag has the same value as XDP_UMEM_TX_SW_CSUM so we could get unexpected SG setups for software Tx checksums. Since csum flag is UAPI, modify value of XDP_UMEM_SG_FLAG. Fixes: d609f3d228a8 ("xsk: add multi-buffer support for sockets sharing umem") Reviewed-by: Björn Töpel <bjorn@kernel.org> Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com> Link: https://patch.msgid.link/20260402154958.562179-4-maciej.fijalkowski@intel.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 93e84fe45b752d17a5a46b306ed78f0133bbc719 ]

Currently xp_assign_dev_shared() is missing XDP_USE_SG being propagated
to flags so set it in order to preserve mtu check that is supposed to be
done only when no multi-buffer setup is in picture.

Also, this flag has the same value as XDP_UMEM_TX_SW_CSUM so we could
get unexpected SG setups for software Tx checksums. Since csum flag is
UAPI, modify value of XDP_UMEM_SG_FLAG.

Fixes: d609f3d228a8 ("xsk: add multi-buffer support for sockets sharing umem")
Reviewed-by: Björn Töpel <bjorn@kernel.org>
Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Link: https://patch.msgid.link/20260402154958.562179-4-maciej.fijalkowski@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>