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Wed, 17 Sep 2025 18:42:26 GMT Received: from smtpav04.wdc07v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 8D6E658050; Wed, 17 Sep 2025 18:42:26 +0000 (GMT) Received: from smtpav04.wdc07v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id CF1B958052; Wed, 17 Sep 2025 18:42:24 +0000 (GMT) Received: from a3560036.lnxne.boe (unknown [9.152.108.100]) by smtpav04.wdc07v.mail.ibm.com (Postfix) with ESMTP; Wed, 17 Sep 2025 18:42:24 +0000 (GMT) From: Sidraya Jayagond To: kuba@kernel.org, andrew+netdev@lunn.ch, davem@davemloft.net, pabeni@redhat.com, horms@kernel.org, alibuda@linux.alibaba.com, dust.li@linux.alibaba.com, wenjia@linux.ibm.com, mjambigi@linux.ibm.com, tonylu@linux.alibaba.com, guwen@linux.alibaba.com Cc: netdev@vger.kernel.org, linux-s390@vger.kernel.org, linux-rdma@vger.kernel.org, Sidraya Jayagond Subject: [PATCH net] net/smc: fix warning in smc_rx_splice() when calling get_page() Date: Wed, 17 Sep 2025 20:42:20 +0200 Message-ID: <20250917184220.801066-1-sidraya@linux.ibm.com> X-Mailer: git-send-email 2.49.0 Precedence: bulk X-Mailing-List: linux-rdma@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwOTE2MDIwNCBTYWx0ZWRfX2+CbK4IC47Rn jHWdDwuPYk6CNOheWhapPHWjtpaBAqdpzaO6h8LPV81V9f+R0o0OxBHQWHjfxWASotsJ55nwaHK tRQ0XQc26sCjigt0h4PALN+8yFlqgEs1PyjS+cjj+2DPnmOO/tnsePgGzeC3x7V4CYComAs9021 VGeVfUe9CTXqPucERxCU0iSqhTtTK3ruSvPreqi1Y/VllPx4ZVyhjWnk0JzjdFTEwdl1hrtLiiL eilfxe79N3IlD2MpPt00Xfr3vBhG3oZRmDNPnOtj9XbTU4vS1VId2aE6ywLh8mXHv2AQ2EnA+8H soxaSRmHstDZtr2Ch5nauaahlqKj0C1qzE/FBA1ZVmeQChxbQDqicZVjLIeTnH4uyLXzik5HCgO FrLF+W6S X-Proofpoint-ORIG-GUID: kco9-Jjn9a2PjTbvShXfph2LF4VijF9T X-Proofpoint-GUID: Ogats12SsLMDZ1X-zxw-rF9lnUJuxn0m X-Authority-Analysis: v=2.4 cv=cNzgskeN c=1 sm=1 tr=0 ts=68cb0115 cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=yJojWOMRYYMA:10 a=VnNF1IyMAAAA:8 a=3kUJVLf2yPifrhjWNHsA:9 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1117,Hydra:6.1.9,FMLib:17.12.80.40 definitions=2025-09-17_01,2025-09-17_02,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 clxscore=1011 spamscore=0 bulkscore=0 malwarescore=0 adultscore=0 priorityscore=1501 impostorscore=0 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2507300000 definitions=main-2509160204 smc_lo_register_dmb() allocates DMB buffers with kzalloc(), which are later passed to get_page() in smc_rx_splice(). Since kmalloc memory is not page-backed, this triggers WARN_ON_ONCE() in get_page() and prevents holding a refcount on the buffer. This can lead to use-after-free if the memory is released before splice_to_pipe() completes. Use folio_alloc() instead, ensuring DMBs are page-backed and safe for get_page(). WARNING: CPU: 18 PID: 12152 at ./include/linux/mm.h:1330 smc_rx_splice+0xaf8/0xe20 [smc] CPU: 18 UID: 0 PID: 12152 Comm: smcapp Kdump: loaded Not tainted 6.17.0-rc3-11705-g9cf4672ecfee #10 NONE Hardware name: IBM 3931 A01 704 (z/VM 7.4.0) Krnl PSW : 0704e00180000000 000793161032696c (smc_rx_splice+0xafc/0xe20 [smc]) R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:3 CC:2 PM:0 RI:0 EA:3 Krnl GPRS: 0000000000000000 001cee80007d3001 00077400000000f8 0000000000000005 0000000000000001 001cee80007d3006 0007740000001000 001c000000000000 000000009b0c99e0 0000000000001000 001c0000000000f8 001c000000000000 000003ffcc6f7c88 0007740003e98000 0007931600000005 000792969b2ff7b8 Krnl Code: 0007931610326960: af000000 mc 0,0 0007931610326964: a7f4ff43 brc 15,00079316103267ea #0007931610326968: af000000 mc 0,0 >000793161032696c: a7f4ff3f brc 15,00079316103267ea 0007931610326970: e320f1000004 lg %r2,256(%r15) 0007931610326976: c0e53fd1b5f5 brasl %r14,000793168fd5d560 000793161032697c: a7f4fbb5 brc 15,00079316103260e6 0007931610326980: b904002b lgr %r2,%r11 Call Trace: smc_rx_splice+0xafc/0xe20 [smc] smc_rx_splice+0x756/0xe20 [smc]) smc_rx_recvmsg+0xa74/0xe00 [smc] smc_splice_read+0x1ce/0x3b0 [smc] sock_splice_read+0xa2/0xf0 do_splice_read+0x198/0x240 splice_file_to_pipe+0x7e/0x110 do_splice+0x59e/0xde0 __do_splice+0x11a/0x2d0 __s390x_sys_splice+0x140/0x1f0 __do_syscall+0x122/0x280 system_call+0x6e/0x90 Last Breaking-Event-Address: smc_rx_splice+0x960/0xe20 [smc] ---[ end trace 0000000000000000 ]--- Fixes: f7a22071dbf3 ("net/smc: implement DMB-related operations of loopback-ism") Reviewed-by: Mahanta Jambigi Signed-off-by: Sidraya Jayagond --- net/smc/smc_loopback.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff --git a/net/smc/smc_loopback.c b/net/smc/smc_loopback.c index 0eb00bbefd17..77cc1c6dc3e9 100644 --- a/net/smc/smc_loopback.c +++ b/net/smc/smc_loopback.c @@ -56,6 +56,7 @@ static int smc_lo_register_dmb(struct smcd_dev *smcd, struct smcd_dmb *dmb, { struct smc_lo_dmb_node *dmb_node, *tmp_node; struct smc_lo_dev *ldev = smcd->priv; + struct folio *folio; int sba_idx, rc; /* check space for new dmb */ @@ -74,13 +75,16 @@ static int smc_lo_register_dmb(struct smcd_dev *smcd, struct smcd_dmb *dmb, dmb_node->sba_idx = sba_idx; dmb_node->len = dmb->dmb_len; - dmb_node->cpu_addr = kzalloc(dmb_node->len, GFP_KERNEL | - __GFP_NOWARN | __GFP_NORETRY | - __GFP_NOMEMALLOC); - if (!dmb_node->cpu_addr) { + + /* not critical; fail under memory pressure and fallback to TCP */ + folio = folio_alloc(GFP_KERNEL | __GFP_NOWARN | __GFP_NOMEMALLOC | + __GFP_NORETRY | __GFP_ZERO, + get_order(dmb_node->len)); + if (!folio) { rc = -ENOMEM; goto err_node; } + dmb_node->cpu_addr = folio_address(folio); dmb_node->dma_addr = SMC_DMA_ADDR_INVALID; refcount_set(&dmb_node->refcnt, 1); @@ -122,7 +126,7 @@ static void __smc_lo_unregister_dmb(struct smc_lo_dev *ldev, write_unlock_bh(&ldev->dmb_ht_lock); clear_bit(dmb_node->sba_idx, ldev->sba_idx_mask); - kvfree(dmb_node->cpu_addr); + folio_put(virt_to_folio(dmb_node->cpu_addr)); kfree(dmb_node); if (atomic_dec_and_test(&ldev->dmb_cnt)) -- 2.49.0