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target: Fix possible integer underflow in UNMAP emulation

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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>
This commit is contained in:
Roland Dreier 2012-07-16 15:34:24 -07:00 committed by Nicholas Bellinger
parent 1a5fa4576e
commit b7fc7f3777
1 changed files with 10 additions and 10 deletions
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20
drivers/target/target_core_iblock.c
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@ -325,24 +325,24 @@ static int iblock_execute_unmap(struct se_cmd *cmd)
struct iblock_dev *ibd = dev->dev_ptr; struct iblock_dev *ibd = dev->dev_ptr;
unsigned char *buf, *ptr = NULL; unsigned char *buf, *ptr = NULL;
sector_t lba; sector_t lba;
unsigned int size = cmd->data_length, range; int size = cmd->data_length;
int ret = 0, offset; u32 range;
unsigned short dl, bd_dl; int ret = 0;
int dl, bd_dl;
/* First UNMAP block descriptor starts at 8 byte offset */
offset = 8;
size -= 8;
buf = transport_kmap_data_sg(cmd); buf = transport_kmap_data_sg(cmd);
dl = get_unaligned_be16(&buf[0]); dl = get_unaligned_be16(&buf[0]);
bd_dl = get_unaligned_be16(&buf[2]); bd_dl = get_unaligned_be16(&buf[2]);
ptr = &buf[offset]; size = min(size - 8, bd_dl);
pr_debug("UNMAP: Sub: %s Using dl: %hu bd_dl: %hu size: %hu"
/* 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); " ptr: %p\n", dev->transport->name, dl, bd_dl, size, ptr);
while (size) { while (size >= 16) {
lba = get_unaligned_be64(&ptr[0]); lba = get_unaligned_be64(&ptr[0]);
range = get_unaligned_be32(&ptr[8]); range = get_unaligned_be32(&ptr[8]);
pr_debug("UNMAP: Using lba: %llu and range: %u\n", pr_debug("UNMAP: Using lba: %llu and range: %u\n",