From 267a6ad4aefaafbde607804c60945bcf97f91c1b Mon Sep 17 00:00:00 2001 From: Huajun Li Date: Sun, 12 Feb 2012 19:59:14 +0800 Subject: [PATCH] [SCSI] scsi_scan: Fix 'Poison overwritten' warning caused by using freed 'shost' In do_scan_async(), calling scsi_autopm_put_host(shost) may reference freed shost, and cause Posison overwitten warning. Yes, this case can happen, for example, an USB is disconnected just when do_scan_async() thread starts to run, then scsi_host_put() called in scsi_finish_async_scan() will lead to shost be freed(because the refcount of shost->shost_gendev decreases to 1 after USB disconnects), at this point, if references shost again, system will show following warning msg. To make scsi_autopm_put_host(shost) always reference a valid shost, put it just before scsi_host_put() in function scsi_finish_async_scan(). [ 299.281565] ============================================================================= [ 299.281634] BUG kmalloc-4096 (Tainted: G I ): Poison overwritten [ 299.281682] ----------------------------------------------------------------------------- [ 299.281684] [ 299.281752] INFO: 0xffff880056c305d0-0xffff880056c305d0. First byte 0x6a instead of 0x6b [ 299.281816] INFO: Allocated in scsi_host_alloc+0x4a/0x490 age=1688 cpu=1 pid=2004 [ 299.281870] __slab_alloc+0x617/0x6c1 [ 299.281901] __kmalloc+0x28c/0x2e0 [ 299.281931] scsi_host_alloc+0x4a/0x490 [ 299.281966] usb_stor_probe1+0x5b/0xc40 [usb_storage] [ 299.282010] storage_probe+0xa4/0xe0 [usb_storage] [ 299.282062] usb_probe_interface+0x172/0x330 [usbcore] [ 299.282105] driver_probe_device+0x257/0x3b0 [ 299.282138] __driver_attach+0x103/0x110 [ 299.282171] bus_for_each_dev+0x8e/0xe0 [ 299.282201] driver_attach+0x26/0x30 [ 299.282230] bus_add_driver+0x1c4/0x430 [ 299.282260] driver_register+0xb6/0x230 [ 299.282298] usb_register_driver+0xe5/0x270 [usbcore] [ 299.282337] 0xffffffffa04ab03d [ 299.282364] do_one_initcall+0x47/0x230 [ 299.282396] sys_init_module+0xa0f/0x1fe0 [ 299.282429] INFO: Freed in scsi_host_dev_release+0x18a/0x1d0 age=85 cpu=0 pid=2008 [ 299.282482] __slab_free+0x3c/0x2a1 [ 299.282510] kfree+0x296/0x310 [ 299.282536] scsi_host_dev_release+0x18a/0x1d0 [ 299.282574] device_release+0x74/0x100 [ 299.282606] kobject_release+0xc7/0x2a0 [ 299.282637] kobject_put+0x54/0xa0 [ 299.282668] put_device+0x27/0x40 [ 299.282694] scsi_host_put+0x1d/0x30 [ 299.282723] do_scan_async+0x1fc/0x2b0 [ 299.282753] kthread+0xdf/0xf0 [ 299.282782] kernel_thread_helper+0x4/0x10 [ 299.282817] INFO: Slab 0xffffea00015b0c00 objects=7 used=7 fp=0x (null) flags=0x100000000004080 [ 299.282882] INFO: Object 0xffff880056c30000 @offset=0 fp=0x (null) [ 299.282884] ... Signed-off-by: Huajun Li Cc: stable@kernel.org Acked-by: Alan Stern Signed-off-by: James Bottomley --- drivers/scsi/scsi_scan.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c index 89da43f73c00..29c4c0480976 100644 --- a/drivers/scsi/scsi_scan.c +++ b/drivers/scsi/scsi_scan.c @@ -1815,6 +1815,7 @@ static void scsi_finish_async_scan(struct async_scan_data *data) } spin_unlock(&async_scan_lock); + scsi_autopm_put_host(shost); scsi_host_put(shost); kfree(data); } @@ -1841,7 +1842,6 @@ static int do_scan_async(void *_data) do_scsi_scan_host(shost); scsi_finish_async_scan(data); - scsi_autopm_put_host(shost); return 0; } @@ -1869,7 +1869,7 @@ void scsi_scan_host(struct Scsi_Host *shost) p = kthread_run(do_scan_async, data, "scsi_scan_%d", shost->host_no); if (IS_ERR(p)) do_scan_async(data); - /* scsi_autopm_put_host(shost) is called in do_scan_async() */ + /* scsi_autopm_put_host(shost) is called in scsi_finish_async_scan() */ } EXPORT_SYMBOL(scsi_scan_host); -- 2.30.2