| Message ID | 1636056397-13151-1-git-send-email-george.kennedy@oracle.com (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
| Series | [v2] scsi: scsi_debug: don't call kcalloc if size arg is zero | expand |
On 2021-11-04 4:06 p.m., George Kennedy wrote: > If the size arg to kcalloc() is zero, it returns ZERO_SIZE_PTR. > Because of that, for a following NULL pointer check to work > on the returned pointer, kcalloc() must not be called with the > size arg equal to zero. Return early without error before the > kcalloc() call if size arg is zero. > > BUG: KASAN: null-ptr-deref in memcpy include/linux/fortify-string.h:191 [inline] > BUG: KASAN: null-ptr-deref in sg_copy_buffer+0x138/0x240 lib/scatterlist.c:974 > Write of size 4 at addr 0000000000000010 by task syz-executor.1/22789 > > CPU: 1 PID: 22789 Comm: syz-executor.1 Not tainted 5.15.0-syzk #1 > Hardware name: Red Hat KVM, BIOS 1.13.0-2 > Call Trace: > __dump_stack lib/dump_stack.c:88 [inline] > dump_stack_lvl+0x89/0xb5 lib/dump_stack.c:106 > __kasan_report mm/kasan/report.c:446 [inline] > kasan_report.cold.14+0x112/0x117 mm/kasan/report.c:459 > check_region_inline mm/kasan/generic.c:183 [inline] > kasan_check_range+0x1a3/0x210 mm/kasan/generic.c:189 > memcpy+0x3b/0x60 mm/kasan/shadow.c:66 > memcpy include/linux/fortify-string.h:191 [inline] > sg_copy_buffer+0x138/0x240 lib/scatterlist.c:974 > do_dout_fetch drivers/scsi/scsi_debug.c:2954 [inline] > do_dout_fetch drivers/scsi/scsi_debug.c:2946 [inline] > resp_verify+0x49e/0x930 drivers/scsi/scsi_debug.c:4276 > schedule_resp+0x4d8/0x1a70 drivers/scsi/scsi_debug.c:5478 > scsi_debug_queuecommand+0x8c9/0x1ec0 drivers/scsi/scsi_debug.c:7533 > scsi_dispatch_cmd drivers/scsi/scsi_lib.c:1520 [inline] > scsi_queue_rq+0x16b0/0x2d40 drivers/scsi/scsi_lib.c:1699 > blk_mq_dispatch_rq_list+0xb9b/0x2700 block/blk-mq.c:1639 > __blk_mq_sched_dispatch_requests+0x28f/0x590 block/blk-mq-sched.c:325 > blk_mq_sched_dispatch_requests+0x105/0x190 block/blk-mq-sched.c:358 > __blk_mq_run_hw_queue+0xe5/0x150 block/blk-mq.c:1761 > __blk_mq_delay_run_hw_queue+0x4f8/0x5c0 block/blk-mq.c:1838 > blk_mq_run_hw_queue+0x18d/0x350 block/blk-mq.c:1891 > blk_mq_sched_insert_request+0x3db/0x4e0 block/blk-mq-sched.c:474 > blk_execute_rq_nowait+0x16b/0x1c0 block/blk-exec.c:62 > blk_execute_rq+0xdb/0x360 block/blk-exec.c:102 > sg_scsi_ioctl drivers/scsi/scsi_ioctl.c:621 [inline] > scsi_ioctl+0x8bb/0x15c0 drivers/scsi/scsi_ioctl.c:930 > sg_ioctl_common+0x172d/0x2710 drivers/scsi/sg.c:1112 > sg_ioctl+0xa2/0x180 drivers/scsi/sg.c:1165 > vfs_ioctl fs/ioctl.c:51 [inline] > __do_sys_ioctl fs/ioctl.c:874 [inline] > __se_sys_ioctl fs/ioctl.c:860 [inline] > __x64_sys_ioctl+0x19d/0x220 fs/ioctl.c:860 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x3a/0x80 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x44/0xae > > Reported-by: syzkaller <syzkaller@googlegroups.com> > Signed-off-by: George Kennedy <george.kennedy@oracle.com> Acked-by: Douglas Gilbert <dgilbert@interlog.com> --- Reference: sbc5r01.pdf [at t10.org] for VERIFY(10) 5.36 page 212: "A VERIFICATION LENGTH field set to zero specifies that no logical blocks shall be transferred or verified. This condition shall not be considered an error." NVMe gets around this with "zero-based" counts (i.e. 0 means transfer and Verify 1 block!). IMO the cure is worse than the disease. For example you have uint16_t for the count of blocks to Verify, do some calculation for the count but forget to check the answer for 0. Next you build the NVMe Verify command and subtract 1 from count and place it in the Verify NLB field (cause its "0-based"). The calculation did yield 0, so after the subtraction of 1, you pass 0xffff to the NLB field. Why does that Verify command take so long? > --- > drivers/scsi/scsi_debug.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c > index 40b473e..3e97efc 100644 > --- a/drivers/scsi/scsi_debug.c > +++ b/drivers/scsi/scsi_debug.c > @@ -4258,6 +4258,8 @@ static int resp_verify(struct scsi_cmnd *scp, struct sdebug_dev_info *devip) > mk_sense_invalid_opcode(scp); > return check_condition_result; > } > + if (vnum == 0) > + return 0; /* not an error */ > a_num = is_bytchk3 ? 1 : vnum; > /* Treat following check like one for read (i.e. no write) access */ > ret = check_device_access_params(scp, lba, a_num, false); > @@ -4321,6 +4323,8 @@ static int resp_report_zones(struct scsi_cmnd *scp, > } > zs_lba = get_unaligned_be64(cmd + 2); > alloc_len = get_unaligned_be32(cmd + 10); > + if (alloc_len == 0) > + return 0; /* not an error */ > rep_opts = cmd[14] & 0x3f; > partial = cmd[14] & 0x80; > >
George, > If the size arg to kcalloc() is zero, it returns ZERO_SIZE_PTR. > Because of that, for a following NULL pointer check to work on the > returned pointer, kcalloc() must not be called with the size arg equal > to zero. Return early without error before the kcalloc() call if size > arg is zero. Applied to 5.16/scsi-staging, thanks!
diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c index 40b473e..3e97efc 100644 --- a/drivers/scsi/scsi_debug.c +++ b/drivers/scsi/scsi_debug.c @@ -4258,6 +4258,8 @@ static int resp_verify(struct scsi_cmnd *scp, struct sdebug_dev_info *devip) mk_sense_invalid_opcode(scp); return check_condition_result; } + if (vnum == 0) + return 0; /* not an error */ a_num = is_bytchk3 ? 1 : vnum; /* Treat following check like one for read (i.e. no write) access */ ret = check_device_access_params(scp, lba, a_num, false); @@ -4321,6 +4323,8 @@ static int resp_report_zones(struct scsi_cmnd *scp, } zs_lba = get_unaligned_be64(cmd + 2); alloc_len = get_unaligned_be32(cmd + 10); + if (alloc_len == 0) + return 0; /* not an error */ rep_opts = cmd[14] & 0x3f; partial = cmd[14] & 0x80;
If the size arg to kcalloc() is zero, it returns ZERO_SIZE_PTR. Because of that, for a following NULL pointer check to work on the returned pointer, kcalloc() must not be called with the size arg equal to zero. Return early without error before the kcalloc() call if size arg is zero. BUG: KASAN: null-ptr-deref in memcpy include/linux/fortify-string.h:191 [inline] BUG: KASAN: null-ptr-deref in sg_copy_buffer+0x138/0x240 lib/scatterlist.c:974 Write of size 4 at addr 0000000000000010 by task syz-executor.1/22789 CPU: 1 PID: 22789 Comm: syz-executor.1 Not tainted 5.15.0-syzk #1 Hardware name: Red Hat KVM, BIOS 1.13.0-2 Call Trace: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x89/0xb5 lib/dump_stack.c:106 __kasan_report mm/kasan/report.c:446 [inline] kasan_report.cold.14+0x112/0x117 mm/kasan/report.c:459 check_region_inline mm/kasan/generic.c:183 [inline] kasan_check_range+0x1a3/0x210 mm/kasan/generic.c:189 memcpy+0x3b/0x60 mm/kasan/shadow.c:66 memcpy include/linux/fortify-string.h:191 [inline] sg_copy_buffer+0x138/0x240 lib/scatterlist.c:974 do_dout_fetch drivers/scsi/scsi_debug.c:2954 [inline] do_dout_fetch drivers/scsi/scsi_debug.c:2946 [inline] resp_verify+0x49e/0x930 drivers/scsi/scsi_debug.c:4276 schedule_resp+0x4d8/0x1a70 drivers/scsi/scsi_debug.c:5478 scsi_debug_queuecommand+0x8c9/0x1ec0 drivers/scsi/scsi_debug.c:7533 scsi_dispatch_cmd drivers/scsi/scsi_lib.c:1520 [inline] scsi_queue_rq+0x16b0/0x2d40 drivers/scsi/scsi_lib.c:1699 blk_mq_dispatch_rq_list+0xb9b/0x2700 block/blk-mq.c:1639 __blk_mq_sched_dispatch_requests+0x28f/0x590 block/blk-mq-sched.c:325 blk_mq_sched_dispatch_requests+0x105/0x190 block/blk-mq-sched.c:358 __blk_mq_run_hw_queue+0xe5/0x150 block/blk-mq.c:1761 __blk_mq_delay_run_hw_queue+0x4f8/0x5c0 block/blk-mq.c:1838 blk_mq_run_hw_queue+0x18d/0x350 block/blk-mq.c:1891 blk_mq_sched_insert_request+0x3db/0x4e0 block/blk-mq-sched.c:474 blk_execute_rq_nowait+0x16b/0x1c0 block/blk-exec.c:62 blk_execute_rq+0xdb/0x360 block/blk-exec.c:102 sg_scsi_ioctl drivers/scsi/scsi_ioctl.c:621 [inline] scsi_ioctl+0x8bb/0x15c0 drivers/scsi/scsi_ioctl.c:930 sg_ioctl_common+0x172d/0x2710 drivers/scsi/sg.c:1112 sg_ioctl+0xa2/0x180 drivers/scsi/sg.c:1165 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:874 [inline] __se_sys_ioctl fs/ioctl.c:860 [inline] __x64_sys_ioctl+0x19d/0x220 fs/ioctl.c:860 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x3a/0x80 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae Reported-by: syzkaller <syzkaller@googlegroups.com> Signed-off-by: George Kennedy <george.kennedy@oracle.com> --- drivers/scsi/scsi_debug.c | 4 ++++ 1 file changed, 4 insertions(+)