5.4-stable review patch. If anyone has any objections, please let me know.
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From: Wang Liang wangliang74@huawei.com
[ Upstream commit b0531cdba5029f897da5156815e3bdafe1e9b88d ]
Similar to previous commit 2a934fdb01db ("media: v4l2-dev: fix error handling in __video_register_device()"), the release hook should be set before device_register(). Otherwise, when device_register() return error and put_device() try to callback the release function, the below warning may happen.
------------[ cut here ]------------ WARNING: CPU: 1 PID: 4760 at drivers/base/core.c:2567 device_release+0x1bd/0x240 drivers/base/core.c:2567 Modules linked in: CPU: 1 UID: 0 PID: 4760 Comm: syz.4.914 Not tainted 6.17.0-rc3+ #1 NONE RIP: 0010:device_release+0x1bd/0x240 drivers/base/core.c:2567 Call Trace: <TASK> kobject_cleanup+0x136/0x410 lib/kobject.c:689 kobject_release lib/kobject.c:720 [inline] kref_put include/linux/kref.h:65 [inline] kobject_put+0xe9/0x130 lib/kobject.c:737 put_device+0x24/0x30 drivers/base/core.c:3797 pps_register_cdev+0x2da/0x370 drivers/pps/pps.c:402 pps_register_source+0x2f6/0x480 drivers/pps/kapi.c:108 pps_tty_open+0x190/0x310 drivers/pps/clients/pps-ldisc.c:57 tty_ldisc_open+0xa7/0x120 drivers/tty/tty_ldisc.c:432 tty_set_ldisc+0x333/0x780 drivers/tty/tty_ldisc.c:563 tiocsetd drivers/tty/tty_io.c:2429 [inline] tty_ioctl+0x5d1/0x1700 drivers/tty/tty_io.c:2728 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:598 [inline] __se_sys_ioctl fs/ioctl.c:584 [inline] __x64_sys_ioctl+0x194/0x210 fs/ioctl.c:584 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x5f/0x2a0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x76/0x7e </TASK>
Before commit c79a39dc8d06 ("pps: Fix a use-after-free"), pps_register_cdev() call device_create() to create pps->dev, which will init dev->release to device_create_release(). Now the comment is outdated, just remove it.
Thanks for the reminder from Calvin Owens, 'kfree_pps' should be removed in pps_register_source() to avoid a double free in the failure case.
Link: https://lore.kernel.org/all/20250827065010.3208525-1-wangliang74@huawei.com/ Fixes: c79a39dc8d06 ("pps: Fix a use-after-free") Signed-off-by: Wang Liang wangliang74@huawei.com Reviewed-By: Calvin Owens calvin@wbinvd.org Link: https://lore.kernel.org/r/20250830075023.3498174-1-wangliang74@huawei.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/pps/kapi.c | 5 +---- drivers/pps/pps.c | 5 ++--- 2 files changed, 3 insertions(+), 7 deletions(-)
diff --git a/drivers/pps/kapi.c b/drivers/pps/kapi.c index 92d1b62ea239d..e9389876229ea 100644 --- a/drivers/pps/kapi.c +++ b/drivers/pps/kapi.c @@ -109,16 +109,13 @@ struct pps_device *pps_register_source(struct pps_source_info *info, if (err < 0) { pr_err("%s: unable to create char device\n", info->name); - goto kfree_pps; + goto pps_register_source_exit; }
dev_dbg(&pps->dev, "new PPS source %s\n", info->name);
return pps;
-kfree_pps: - kfree(pps); - pps_register_source_exit: pr_err("%s: unable to register source\n", info->name);
diff --git a/drivers/pps/pps.c b/drivers/pps/pps.c index ea966fc67d287..dbeb67ffebf33 100644 --- a/drivers/pps/pps.c +++ b/drivers/pps/pps.c @@ -375,6 +375,7 @@ int pps_register_cdev(struct pps_device *pps) pps->info.name); err = -EBUSY; } + kfree(pps); goto out_unlock; } pps->id = err; @@ -384,13 +385,11 @@ int pps_register_cdev(struct pps_device *pps) pps->dev.devt = MKDEV(pps_major, pps->id); dev_set_drvdata(&pps->dev, pps); dev_set_name(&pps->dev, "pps%d", pps->id); + pps->dev.release = pps_device_destruct; err = device_register(&pps->dev); if (err) goto free_idr;
- /* Override the release function with our own */ - pps->dev.release = pps_device_destruct; - pr_debug("source %s got cdev (%d:%d)\n", pps->info.name, pps_major, pps->id);