Messages in this thread Patch in this message | | | Date | Thu, 4 Nov 2021 13:22:34 -0400 | Subject | Re: [PATCH] scsi: scsi_debug: fix return checks for kcalloc | From | George Kennedy <> |
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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
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