target: Fix possible integer underflow in UNMAP emulation
It's possible for an initiator to send us an UNMAP command with a
descriptor that is less than 8 bytes; in that case it's really bad for
us to set an unsigned int to that value, subtract 8 from it, and then
use that as a limit for our loop (since the value will wrap around to
a huge positive value).
Fix this by making size be signed and only looping if size >= 16 (ie
if we have at least a full descriptor available).
Also remove offset as an obfuscated name for the constant 8.
Signed-off-by: Roland Dreier <roland@purestorage.com>
Cc: stable@vger.kernel.org
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
diff --git a/drivers/target/target_core_iblock.c b/drivers/target/target_core_iblock.c
index e6d08ee..2efd70c 100644
--- a/drivers/target/target_core_iblock.c
+++ b/drivers/target/target_core_iblock.c
@@ -325,24 +325,24 @@
struct iblock_dev *ibd = dev->dev_ptr;
unsigned char *buf, *ptr = NULL;
sector_t lba;
- unsigned int size = cmd->data_length, range;
- int ret = 0, offset;
- unsigned short dl, bd_dl;
-
- /* First UNMAP block descriptor starts at 8 byte offset */
- offset = 8;
- size -= 8;
+ int size = cmd->data_length;
+ u32 range;
+ int ret = 0;
+ int dl, bd_dl;
buf = transport_kmap_data_sg(cmd);
dl = get_unaligned_be16(&buf[0]);
bd_dl = get_unaligned_be16(&buf[2]);
- ptr = &buf[offset];
- pr_debug("UNMAP: Sub: %s Using dl: %hu bd_dl: %hu size: %hu"
+ size = min(size - 8, bd_dl);
+
+ /* First UNMAP block descriptor starts at 8 byte offset */
+ ptr = &buf[8];
+ pr_debug("UNMAP: Sub: %s Using dl: %u bd_dl: %u size: %u"
" ptr: %p\n", dev->transport->name, dl, bd_dl, size, ptr);
- while (size) {
+ while (size >= 16) {
lba = get_unaligned_be64(&ptr[0]);
range = get_unaligned_be32(&ptr[8]);
pr_debug("UNMAP: Using lba: %llu and range: %u\n",