Re: [PATCH v3 linux-next] scsi: scsi_debug: fix type in min_t to avoid stack OOB

Douglas Gilbert <dgilbert@xxxxxxxxxxxx> · Fri, 5 Nov 2021 20:20:56 -0400

On 2021-11-05 11:10 a.m., George Kennedy wrote:
Change min_t() to use type "u32" instead of type "int" to
avoid stack out of bounds. With min_t() type "int" the values get
sign extended and the larger value gets used causing stack out of bounds.

BUG: KASAN: stack-out-of-bounds in memcpy include/linux/fortify-string.h:191 [inline]
BUG: KASAN: stack-out-of-bounds in sg_copy_buffer+0x1de/0x240 lib/scatterlist.c:976
Read of size 127 at addr ffff888072607128 by task syz-executor.7/18707

CPU: 1 PID: 18707 Comm: syz-executor.7 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
  print_address_description.constprop.9+0x28/0x160 mm/kasan/report.c:256
  __kasan_report mm/kasan/report.c:442 [inline]
  kasan_report.cold.14+0x7d/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+0x23/0x60 mm/kasan/shadow.c:65
  memcpy include/linux/fortify-string.h:191 [inline]
  sg_copy_buffer+0x1de/0x240 lib/scatterlist.c:976
  sg_copy_from_buffer+0x33/0x40 lib/scatterlist.c:1000
  fill_from_dev_buffer.part.34+0x82/0x130 drivers/scsi/scsi_debug.c:1162
  fill_from_dev_buffer drivers/scsi/scsi_debug.c:1888 [inline]
  resp_readcap16+0x365/0x3b0 drivers/scsi/scsi_debug.c:1887
  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
  sg_common_write.isra.18+0xeb3/0x2000 drivers/scsi/sg.c:836
  sg_new_write.isra.19+0x570/0x8c0 drivers/scsi/sg.c:774
  sg_ioctl_common+0x14d6/0x2710 drivers/scsi/sg.c:939
  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@xxxxxxxxxxxxxxxx>
Signed-off-by: George Kennedy <george.kennedy@xxxxxxxxxx>

Acked-by: Douglas Gilbert <dgilbert@xxxxxxxxxxxx>

---
  drivers/scsi/scsi_debug.c | 27 +++++++++++++++------------
  1 file changed, 15 insertions(+), 12 deletions(-)

diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
index 06e7266..3b5ee42 100644
--- a/drivers/scsi/scsi_debug.c
+++ b/drivers/scsi/scsi_debug.c
@@ -1189,7 +1189,7 @@ static int p_fill_from_dev_buffer(struct scsi_cmnd *scp, const void *arr,
  		 __func__, off_dst, scsi_bufflen(scp), act_len,
  		 scsi_get_resid(scp));
  	n = scsi_bufflen(scp) - (off_dst + act_len);
-	scsi_set_resid(scp, min_t(int, scsi_get_resid(scp), n));
+	scsi_set_resid(scp, min_t(u32, scsi_get_resid(scp), n));
  	return 0;
  }
  
@@ -1562,7 +1562,8 @@ static int resp_inquiry(struct scsi_cmnd *scp, struct sdebug_dev_info *devip)
  	unsigned char pq_pdt;
  	unsigned char *arr;
  	unsigned char *cmd = scp->cmnd;
-	int alloc_len, n, ret;
+	u32 alloc_len, n;
+	int ret;
  	bool have_wlun, is_disk, is_zbc, is_disk_zbc;
  
  	alloc_len = get_unaligned_be16(cmd + 3);
@@ -1714,7 +1715,7 @@ static int resp_inquiry(struct scsi_cmnd *scp, struct sdebug_dev_info *devip)
  	}
  	put_unaligned_be16(0x2100, arr + n);	/* SPL-4 no version claimed */
  	ret = fill_from_dev_buffer(scp, arr,
-			    min_t(int, alloc_len, SDEBUG_LONG_INQ_SZ));
+			    min_t(u32, alloc_len, SDEBUG_LONG_INQ_SZ));
  	kfree(arr);
  	return ret;
  }
@@ -1729,8 +1730,8 @@ static int resp_requests(struct scsi_cmnd *scp,
  	unsigned char *cmd = scp->cmnd;
  	unsigned char arr[SCSI_SENSE_BUFFERSIZE];	/* assume >= 18 bytes */
  	bool dsense = !!(cmd[1] & 1);
-	int alloc_len = cmd[4];
-	int len = 18;
+	u32 alloc_len = cmd[4];
+	u32 len = 18;
  	int stopped_state = atomic_read(&devip->stopped);
  
  	memset(arr, 0, sizeof(arr));
@@ -1774,7 +1775,7 @@ static int resp_requests(struct scsi_cmnd *scp,
  			arr[7] = 0xa;
  		}
  	}
-	return fill_from_dev_buffer(scp, arr, min_t(int, len, alloc_len));
+	return fill_from_dev_buffer(scp, arr, min_t(u32, len, alloc_len));
  }
  
  static int resp_start_stop(struct scsi_cmnd *scp, struct sdebug_dev_info *devip)
@@ -2312,7 +2313,8 @@ static int resp_mode_sense(struct scsi_cmnd *scp,
  {
  	int pcontrol, pcode, subpcode, bd_len;
  	unsigned char dev_spec;
-	int alloc_len, offset, len, target_dev_id;
+	u32 alloc_len, offset, len;
+	int target_dev_id;
  	int target = scp->device->id;
  	unsigned char *ap;
  	unsigned char arr[SDEBUG_MAX_MSENSE_SZ];
@@ -2468,7 +2470,7 @@ static int resp_mode_sense(struct scsi_cmnd *scp,
  		arr[0] = offset - 1;
  	else
  		put_unaligned_be16((offset - 2), arr + 0);
-	return fill_from_dev_buffer(scp, arr, min_t(int, alloc_len, offset));
+	return fill_from_dev_buffer(scp, arr, min_t(u32, alloc_len, offset));
  }
  
  #define SDEBUG_MAX_MSELECT_SZ 512
@@ -2583,7 +2585,8 @@ static int resp_ie_l_pg(unsigned char *arr)
  static int resp_log_sense(struct scsi_cmnd *scp,
  			  struct sdebug_dev_info *devip)
  {
-	int ppc, sp, pcode, subpcode, alloc_len, len, n;
+	int ppc, sp, pcode, subpcode;
+	u32 alloc_len, len, n;
  	unsigned char arr[SDEBUG_MAX_LSENSE_SZ];
  	unsigned char *cmd = scp->cmnd;
  
@@ -2653,9 +2656,9 @@ static int resp_log_sense(struct scsi_cmnd *scp,
  		mk_sense_invalid_fld(scp, SDEB_IN_CDB, 3, -1);
  		return check_condition_result;
  	}
-	len = min_t(int, get_unaligned_be16(arr + 2) + 4, alloc_len);
+	len = min_t(u32, get_unaligned_be16(arr + 2) + 4, alloc_len);
  	return fill_from_dev_buffer(scp, arr,
-		    min_t(int, len, SDEBUG_MAX_INQ_ARR_SZ));
+		    min_t(u32, len, SDEBUG_MAX_INQ_ARR_SZ));
  }
  
  static inline bool sdebug_dev_is_zoned(struct sdebug_dev_info *devip)
@@ -4426,7 +4429,7 @@ static int resp_report_zones(struct scsi_cmnd *scp,
  	put_unaligned_be64(sdebug_capacity - 1, arr + 8);
  
  	rep_len = (unsigned long)desc - (unsigned long)arr;
-	ret = fill_from_dev_buffer(scp, arr, min_t(int, alloc_len, rep_len));
+	ret = fill_from_dev_buffer(scp, arr, min_t(u32, alloc_len, rep_len));
  
  fini:
  	read_unlock(macc_lckp);








