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([128.210.0.165]) by smtp.googlemail.com with ESMTPSA id 00721157ae682-798decdd38dsm34981287b3.21.2026.03.08.12.01.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 08 Mar 2026 12:01:24 -0700 (PDT) From: Sungwoo Kim To: Davidlohr Bueso , Jonathan Cameron , Dave Jiang , Alison Schofield , Vishal Verma , Ira Weiny , Dan Williams , Ben Widawsky Cc: daveti@purdue.edu, Sungwoo Kim , Jonathan Cameron , linux-cxl@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] cxl/region: Fix a race bug in delete_region_store Date: Sun, 8 Mar 2026 14:59:58 -0400 Message-ID: <20260308185958.2453707-2-iam@sung-woo.kim> X-Mailer: git-send-email 2.47.3 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" A race exists when two concurrent sysfs writes to delete_region specify the same region name. Both calls succeed in cxl_find_region_by_name() (which only does device_find_child_by_name and takes a reference), and both then proceed to call devm_release_action(). The first call atomically removes and releases the devres entry successfully. The second call finds no matching entry, causing devres_release() to return -ENOENT, which trips the WARN_ON. Fix this by replacing devm_release_action() with devm_remove_action_nowarn() followed by a manual call to unregister_region(). devm_remove_action_nowarn= () removes the devres tracking entry and returns an error code. Reviewed-by: Ira Weiny ------------[ cut here ]------------ WARNING: drivers/base/devres.c:824 at devm_release_action drivers/base/devr= es.c:824 [inline], CPU#0: syz.1.12224/47589 WARNING: drivers/base/devres.c:824 at devm_release_action+0x2b2/0x360 drive= rs/base/devres.c:817, CPU#0: syz.1.12224/47589 Modules linked in: CPU: 0 UID: 0 PID: 47589 Comm: syz.1.12224 Not tainted 6.19.0-g15a37b05f387= #10 PREEMPT(lazy)=20 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.17.0-0-gb52c= a86e094d-prebuilt.qemu.org 04/01/2014 RIP: 0010:devm_release_action drivers/base/devres.c:824 [inline] RIP: 0010:devm_release_action+0x2b2/0x360 drivers/base/devres.c:817 Code: 41 5c 41 5d 41 5e 41 5f e9 86 1a b3 fd e8 86 71 33 fe e8 81 71 33 fe = 48 8b 74 24 08 4c 89 f7 e8 04 34 8a 01 e8 6f 71 33 fe 90 <0f> 0b 90 eb c6 e= 8 64 71 33 fe 90 0f 0b e8 2c f1 71 fe e9 f4 fd ff RSP: 0018:ffff88813e5f7bf8 EFLAGS: 00010282 RAX: 0000000000000125 RBX: dffffc0000000000 RCX: ffffffff835d26a1 RDX: 0000000000080000 RSI: ffffc9000685b000 RDI: ffffffff8e875adf RBP: ffff888101059010 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000001 R11: 0000000000000000 R12: ffff888101059428 R13: ffff888100e05c30 R14: ffff8881010593e8 R15: ffff888101059428 FS: 00007fae6afb46c0(0000) GS:ffff8882a526d000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fae6a12b8c0 CR3: 0000000127f1b005 CR4: 0000000000770ef0 PKRU: 80000000 Call Trace: delete_region_store+0x106/0x1d0 drivers/cxl/core/region.c:2753 dev_attr_store+0x58/0x80 drivers/base/core.c:2437 sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:142 kernfs_fop_write_iter+0x3d6/0x5d0 fs/kernfs/file.c:352 new_sync_write fs/read_write.c:595 [inline] vfs_write+0x68e/0x1050 fs/read_write.c:688 ksys_write+0x12a/0x250 fs/read_write.c:740 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfc/0x670 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fae6a19c669 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 = 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff f= f 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fae6afb4028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007fae6a415fa0 RCX: 00007fae6a19c669 RDX: 0000000000000008 RSI: 0000200000000580 RDI: 0000000000000005 RBP: 00007fae6a232c71 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fae6a416038 R14: 00007fae6a415fa0 R15: 00007ffc10522c58 irq event stamp: 885 hardirqs last enabled at (893): [] __up_console_sem+0x7b= /0x90 kernel/printk/printk.c:347 hardirqs last disabled at (902): [] __up_console_sem+0x60= /0x90 kernel/printk/printk.c:345 softirqs last enabled at (822): [] __do_softirq kernel/s= oftirq.c:656 [inline] softirqs last enabled at (822): [] invoke_softirq kernel= /softirq.c:496 [inline] softirqs last enabled at (822): [] __irq_exit_rcu+0xb3/0= xe0 kernel/softirq.c:723 softirqs last disabled at (811): [] __do_softirq kernel/s= oftirq.c:656 [inline] softirqs last disabled at (811): [] invoke_softirq kernel= /softirq.c:496 [inline] softirqs last disabled at (811): [] __irq_exit_rcu+0xb3/0= xe0 kernel/softirq.c:723 ---[ end trace 0000000000000000 ]--- Fixes: 779dd20cfb56 ("cxl/region: Add region creation support") Signed-off-by: Sungwoo Kim --- drivers/cxl/core/region.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c index 08fa3deef70ab..7ade9aa2aeecc 100644 --- a/drivers/cxl/core/region.c +++ b/drivers/cxl/core/region.c @@ -2745,12 +2745,19 @@ static ssize_t delete_region_store(struct device *d= ev, struct cxl_root_decoder *cxlrd =3D to_cxl_root_decoder(dev); struct cxl_port *port =3D to_cxl_port(dev->parent); struct cxl_region *cxlr; + int err; =20 cxlr =3D cxl_find_region_by_name(cxlrd, buf); if (IS_ERR(cxlr)) return PTR_ERR(cxlr); =20 - devm_release_action(port->uport_dev, unregister_region, cxlr); + err =3D devm_remove_action_nowarn(port->uport_dev, unregister_region, + cxlr); + if (err) { + put_device(&cxlr->dev); + return err; + } + unregister_region(cxlr); put_device(&cxlr->dev); =20 return len; --=20 2.47.3