Thanks Joe,
On 11/4/2021 12:04 PM, Joe Perches wrote:
On Wed, 2021-11-03 at 14:01 -0500, George Kennedy wrote:
Change return checks from kcalloc() to now check for NULL and
ZERO_SIZE_PTR using the ZERO_OR_NULL_PTR macro or the following
crash can occur if ZERO_SIZE_PTR indicator is returned.
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
[]
diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
[]
@@ -3909,7 +3909,7 @@ static int resp_comp_write(struct scsi_cmnd *scp,
return ret;
dnum = 2 * num;
arr = kcalloc(lb_size, dnum, GFP_ATOMIC);
- if (NULL == arr) {
+ if (ZERO_OR_NULL_PTR(arr)) {
mk_sense_buffer(scp, ILLEGAL_REQUEST, INSUFF_RES_ASC,
INSUFF_RES_ASCQ);
return check_condition_result;
This one isn't necessary as num is already tested for non-0 above
this block.
The check for "num" preceding the above does this:
if (0 == num)
return 0; /* degenerate case, not an error */
Shouldn't I use that same size check and "return 0" if size == zero in
the other cases?
@@ -4265,7 +4265,7 @@ static int resp_verify(struct scsi_cmnd *scp, struct sdebug_dev_info *devip)
return ret;
arr = kcalloc(lb_size, vnum, GFP_ATOMIC);
- if (!arr) {
+ if (ZERO_OR_NULL_PTR(arr)) {
mk_sense_buffer(scp, ILLEGAL_REQUEST, INSUFF_RES_ASC,
INSUFF_RES_ASCQ);
return check_condition_result;
Here it's probably clearer code to test vnum == 0 before the kcalloc
and return check_condition_result;
@@ -4334,7 +4334,7 @@ static int resp_report_zones(struct scsi_cmnd *scp,
max_zones);
arr = kcalloc(RZONES_DESC_HD, alloc_len, GFP_ATOMIC);
- if (!arr) {
+ if (ZERO_OR_NULL_PTR(arr)) {
mk_sense_buffer(scp, ILLEGAL_REQUEST, INSUFF_RES_ASC,
INSUFF_RES_ASCQ);
return check_condition_result;
And here test alloc_len == 0 before the kcalloc.
Using your suggested fix (with return 0 instead of return
check_condition_result) the patch would look like this:
diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
index 40b473e..93913d2 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 (0 == vnum)
+ return 0; /* degenerate case, 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 (0 == alloc_len)
+ return 0; /* degenerate case, not an error */
rep_opts = cmd[14] & 0x3f;
partial = cmd[14] & 0x80;
Does the above look ok?
George
