| From 93aa71ad7379900e61c8adff6a710a4c18c7c99b Mon Sep 17 00:00:00 2001 |
| From: Tyrel Datwyler <tyreld@linux.ibm.com> |
| Date: Thu, 1 Jul 2021 13:56:59 -0600 |
| Subject: scsi: core: Fix bad pointer dereference when ehandler kthread is invalid |
| |
| From: Tyrel Datwyler <tyreld@linux.ibm.com> |
| |
| commit 93aa71ad7379900e61c8adff6a710a4c18c7c99b upstream. |
| |
| Commit 66a834d09293 ("scsi: core: Fix error handling of scsi_host_alloc()") |
| changed the allocation logic to call put_device() to perform host cleanup |
| with the assumption that IDA removal and stopping the kthread would |
| properly be performed in scsi_host_dev_release(). However, in the unlikely |
| case that the error handler thread fails to spawn, shost->ehandler is set |
| to ERR_PTR(-ENOMEM). |
| |
| The error handler cleanup code in scsi_host_dev_release() will call |
| kthread_stop() if shost->ehandler != NULL which will always be the case |
| whether the kthread was successfully spawned or not. In the case that it |
| failed to spawn this has the nasty side effect of trying to dereference an |
| invalid pointer when kthread_stop() is called. The following splat provides |
| an example of this behavior in the wild: |
| |
| 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 |
| |
| Fix this be nulling shost->ehandler when the kthread fails to spawn. |
| |
| Link: https://lore.kernel.org/r/20210701195659.3185475-1-tyreld@linux.ibm.com |
| Fixes: 66a834d09293 ("scsi: core: Fix error handling of scsi_host_alloc()") |
| Cc: stable@vger.kernel.org |
| Reviewed-by: Ming Lei <ming.lei@redhat.com> |
| Signed-off-by: Tyrel Datwyler <tyreld@linux.ibm.com> |
| Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| drivers/scsi/hosts.c | 1 + |
| 1 file changed, 1 insertion(+) |
| |
| --- a/drivers/scsi/hosts.c |
| +++ b/drivers/scsi/hosts.c |
| @@ -490,6 +490,7 @@ struct Scsi_Host *scsi_host_alloc(struct |
| shost_printk(KERN_WARNING, shost, |
| "error handler thread failed to spawn, error = %ld\n", |
| PTR_ERR(shost->ehandler)); |
| + shost->ehandler = NULL; |
| goto fail; |
| } |
| |