Re: [PATCH 1/4] scsi: core: fix error handling of scsi_host_alloc
From: Tyrel Datwyler <tyreld@linux.ibm.com>
Date: 2021-06-29 19:23:22
On 6/2/21 6:30 AM, Ming Lei wrote:
After device is initialized via device_initialize(), or its name is set via dev_set_name(), the device has to be freed via put_device(), otherwise device name will be leaked because it is allocated dynamically in dev_set_name(). Fixes the issue by replacing kfree(shost) via put_device(&shost->shost_gendev) which can help to free dev_name(&shost->shost_dev) when host state is in SHOST_CREATED. Meantime needn't to remove IDA and stop the kthread of shost->ehandler in the error handling code.
This statement is incorrect for kthread. If error handler thread failed to spawn the value of shost->ehandler will be ERR_PTR(-ENOMEM) which will pass the "if (shost->ehandler)" check in scsi_host_dev_release() resulting in a kthread_stop() call for a non-existant kthread which triggers a bad pointer dereference. Here is an example splat: scsi host11: error handler thread failed to spawn, error = -4 Kernel attempted to read user page (10c) - exploit attempt? (uid: 0) BUG: Kernel NULL pointer dereference on read at 0x0000010c Faulting instruction address: 0xc00000000818e9a8 Oops: Kernel access of bad area, sig: 11 [#1] LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries Modules linked in: ibmvscsi(+) scsi_transport_srp dm_multipath dm_mirror dm_region hash dm_log dm_mod fuse overlay squashfs loop CPU: 12 PID: 274 Comm: systemd-udevd Not tainted 5.13.0-rc7 #1 NIP: c00000000818e9a8 LR: c0000000089846e8 CTR: 0000000000007ee8 REGS: c000000037d12ea0 TRAP: 0300 Not tainted (5.13.0-rc7) MSR: 800000000280b033 <SF,VEC,VSX,EE,FP,ME,IR,DR,RI,LE> CR: 28228228 XER: 20040001 CFAR: c0000000089846e4 DAR: 000000000000010c DSISR: 40000000 IRQMASK: 0 GPR00: c0000000089846e8 c000000037d13140 c000000009cc1100 fffffffffffffffc GPR04: 0000000000000001 0000000000000000 0000000000000000 c000000037dc0000 GPR08: 0000000000000000 c000000037dc0000 0000000000000001 00000000fffff7ff GPR12: 0000000000008000 c00000000a049000 c000000037d13d00 000000011134d5a0 GPR16: 0000000000001740 c0080000190d0000 c0080000190d1740 c000000009129288 GPR20: c000000037d13bc0 0000000000000001 c000000037d13bc0 c0080000190b7898 GPR24: c0080000190b7708 0000000000000000 c000000033bb2c48 0000000000000000 GPR28: c000000046b28280 0000000000000000 000000000000010c fffffffffffffffc NIP [c00000000818e9a8] kthread_stop+0x38/0x230 LR [c0000000089846e8] scsi_host_dev_release+0x98/0x160 Call Trace: [c000000033bb2c48] 0xc000000033bb2c48 (unreliable) [c0000000089846e8] scsi_host_dev_release+0x98/0x160 [c00000000891e960] device_release+0x60/0x100 [c0000000087e55c4] kobject_release+0x84/0x210 [c00000000891ec78] put_device+0x28/0x40 [c000000008984ea4] scsi_host_alloc+0x314/0x430 [c0080000190b38bc] ibmvscsi_probe+0x54/0xad0 [ibmvscsi] [c000000008110104] vio_bus_probe+0xa4/0x4b0 [c00000000892a860] really_probe+0x140/0x680 [c00000000892aefc] driver_probe_device+0x15c/0x200 [c00000000892b63c] device_driver_attach+0xcc/0xe0 [c00000000892b740] __driver_attach+0xf0/0x200 [c000000008926f28] bus_for_each_dev+0xa8/0x130 [c000000008929ce4] driver_attach+0x34/0x50 [c000000008928fc0] bus_add_driver+0x1b0/0x300 [c00000000892c798] driver_register+0x98/0x1a0 [c00000000810eb60] __vio_register_driver+0x80/0xe0 [c0080000190b4a30] ibmvscsi_module_init+0x9c/0xdc [ibmvscsi] [c0000000080121d0] do_one_initcall+0x60/0x2d0 [c000000008261abc] do_init_module+0x7c/0x320 [c000000008265700] load_module+0x2350/0x25b0 [c000000008265cb4] __do_sys_finit_module+0xd4/0x160 [c000000008031110] system_call_exception+0x150/0x2d0 [c00000000800d35c] system_call_common+0xec/0x278 I'm happy to send a fix, but I see two possible approaches. 1.) Set shost->ehandler = NULL if kthread_run() fails in scsi_host_alloc() or 2.) Test that (shost->ehandler && !IS_ERR(shost->ehandler)) before calling kthread_stop in scsi_host_dev_release() -Tyrel
quoted hunk ↗ jump to hunk
Cc: Bart Van Assche <bvanassche@acm.org> Cc: John Garry <redacted> Cc: Hannes Reinecke <hare@suse.de> Signed-off-by: Ming Lei <redacted> --- drivers/scsi/hosts.c | 23 +++++++++++++---------- 1 file changed, 13 insertions(+), 10 deletions(-)diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c index 624e2582c3df..25cf76e73595 100644 --- a/drivers/scsi/hosts.c +++ b/drivers/scsi/hosts.c@@ -391,8 +391,10 @@ struct Scsi_Host *scsi_host_alloc(struct scsi_host_template *sht, int privsize) mutex_init(&shost->scan_mutex); index = ida_simple_get(&host_index_ida, 0, 0, GFP_KERNEL); - if (index < 0) - goto fail_kfree; + if (index < 0) { + kfree(shost); + return NULL; + } shost->host_no = index; shost->dma_channel = 0xff;@@ -484,7 +486,7 @@ struct Scsi_Host *scsi_host_alloc(struct scsi_host_template *sht, int privsize) shost_printk(KERN_WARNING, shost, "error handler thread failed to spawn, error = %ld\n", PTR_ERR(shost->ehandler)); - goto fail_index_remove; + goto fail; } shost->tmf_work_q = alloc_workqueue("scsi_tmf_%d",@@ -493,17 +495,18 @@ struct Scsi_Host *scsi_host_alloc(struct scsi_host_template *sht, int privsize) if (!shost->tmf_work_q) { shost_printk(KERN_WARNING, shost, "failed to create tmf workq\n"); - goto fail_kthread; + goto fail; } scsi_proc_hostdir_add(shost->hostt); return shost; + fail: + /* + * host state is still SHOST_CREATED, and it is enough to release + * ->shost_gendev since scsi_host_dev_release() can help to free + * dev_name(&shost->shost_dev) + */ + put_device(&shost->shost_gendev); - fail_kthread: - kthread_stop(shost->ehandler); - fail_index_remove: - ida_simple_remove(&host_index_ida, shost->host_no); - fail_kfree: - kfree(shost); return NULL; } EXPORT_SYMBOL(scsi_host_alloc);