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Tue, 25 Nov 2025 11:40:54 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id QG23C8aVJWnUQAAAD6G6ig (envelope-from ); Tue, 25 Nov 2025 11:40:54 +0000 Message-ID: <955e2de1-32f6-42e3-8358-b8574188ce62@suse.de> Date: Tue, 25 Nov 2025 12:40:49 +0100 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net v6] xsk: avoid data corruption on cq descriptor number To: Jason Xing Cc: netdev@vger.kernel.org, csmate@nop.hu, maciej.fijalkowski@intel.com, bpf@vger.kernel.org, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, sdf@fomichev.me, hawk@kernel.org, daniel@iogearbox.net, ast@kernel.org, john.fastabend@gmail.com, magnus.karlsson@intel.com References: <20251124171409.3845-1-fmancera@suse.de> Content-Language: en-US From: Fernando Fernandez Mancera In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Spamd-Result: default: False [-2.80 / 50.00]; BAYES_HAM(-3.00)[100.00%]; SUSPICIOUS_RECIPS(1.50)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FREEMAIL_TO(0.00)[gmail.com]; FUZZY_RATELIMITED(0.00)[rspamd.com]; MIME_TRACE(0.00)[0:+]; ARC_NA(0.00)[]; RCPT_COUNT_TWELVE(0.00)[16]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; FREEMAIL_CC(0.00)[vger.kernel.org,nop.hu,intel.com,davemloft.net,google.com,kernel.org,redhat.com,fomichev.me,iogearbox.net,gmail.com]; RCVD_TLS_ALL(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; TAGGED_RCPT(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo,suse.de:mid,suse.de:email] X-Spam-Flag: NO X-Spam-Score: -2.80 X-Spam-Level: On 11/25/25 12:41 AM, Jason Xing wrote: > On Tue, Nov 25, 2025 at 1:14 AM Fernando Fernandez Mancera > wrote: >> >> Since commit 30f241fcf52a ("xsk: Fix immature cq descriptor >> production"), the descriptor number is stored in skb control block and >> xsk_cq_submit_addr_locked() relies on it to put the umem addrs onto >> pool's completion queue. >> >> skb control block shouldn't be used for this purpose as after transmit >> xsk doesn't have control over it and other subsystems could use it. This >> leads to the following kernel panic due to a NULL pointer dereference. >> >> BUG: kernel NULL pointer dereference, address: 0000000000000000 >> #PF: supervisor read access in kernel mode >> #PF: error_code(0x0000) - not-present page >> PGD 0 P4D 0 >> Oops: Oops: 0000 [#1] SMP NOPTI >> CPU: 2 UID: 1 PID: 927 Comm: p4xsk.bin Not tainted 6.16.12+deb14-cloud-amd64 #1 PREEMPT(lazy) Debian 6.16.12-1 >> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-debian-1.17.0-1 04/01/2014 >> RIP: 0010:xsk_destruct_skb+0xd0/0x180 >> [...] >> Call Trace: >> >> ? napi_complete_done+0x7a/0x1a0 >> ip_rcv_core+0x1bb/0x340 >> ip_rcv+0x30/0x1f0 >> __netif_receive_skb_one_core+0x85/0xa0 >> process_backlog+0x87/0x130 >> __napi_poll+0x28/0x180 >> net_rx_action+0x339/0x420 >> handle_softirqs+0xdc/0x320 >> ? handle_edge_irq+0x90/0x1e0 >> do_softirq.part.0+0x3b/0x60 >> >> >> __local_bh_enable_ip+0x60/0x70 >> __dev_direct_xmit+0x14e/0x1f0 >> __xsk_generic_xmit+0x482/0xb70 >> ? __remove_hrtimer+0x41/0xa0 >> ? __xsk_generic_xmit+0x51/0xb70 >> ? _raw_spin_unlock_irqrestore+0xe/0x40 >> xsk_sendmsg+0xda/0x1c0 >> __sys_sendto+0x1ee/0x200 >> __x64_sys_sendto+0x24/0x30 >> do_syscall_64+0x84/0x2f0 >> ? __pfx_pollwake+0x10/0x10 >> ? __rseq_handle_notify_resume+0xad/0x4c0 >> ? restore_fpregs_from_fpstate+0x3c/0x90 >> ? switch_fpu_return+0x5b/0xe0 >> ? do_syscall_64+0x204/0x2f0 >> ? do_syscall_64+0x204/0x2f0 >> ? do_syscall_64+0x204/0x2f0 >> entry_SYSCALL_64_after_hwframe+0x76/0x7e >> >> [...] >> Kernel panic - not syncing: Fatal exception in interrupt >> Kernel Offset: 0x1c000000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff) >> >> Instead use the skb destructor_arg pointer along with pointer tagging. >> As pointers are always aligned to 8B, use the bottom bit to indicate >> whether this a single address or an allocated struct containing several >> addresses. >> >> Fixes: 30f241fcf52a ("xsk: Fix immature cq descriptor production") >> Closes: https://lore.kernel.org/netdev/0435b904-f44f-48f8-afb0-68868474bf1c@nop.hu/ >> Suggested-by: Jakub Kicinski >> Signed-off-by: Fernando Fernandez Mancera > > Reviewed-by: Jason Xing > > Could you also post a patch on top of net-next as it has diverged from > the net tree? > I think that is handled by maintainers when merging the branches. A repost would be wrong because linux-next.git and linux.git will have a different variant of the same commit.. Please, let me know if I am wrong here. Thanks, Fernando.