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From 8d14ccd4bd5dab58984030c13a71953d396e792d Mon Sep 17 00:00:00 2001
From: Roland Dreier <roland@purestorage.com>
Date: Mon, 16 Jul 2012 15:34:24 -0700
Subject: [PATCH 43/73] target: Fix possible integer underflow in UNMAP
emulation
commit b7fc7f3777582dea85156a821d78a522a0c083aa upstream.
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>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
[bwh: Backported to 3.2: adjust filename, context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/target/target_core_cdb.c | 20 ++++++++++----------
1 files changed, 10 insertions(+), 10 deletions(-)
diff --git a/drivers/target/target_core_cdb.c b/drivers/target/target_core_cdb.c
index b1f5cf0..00f0f7d 100644
--- a/drivers/target/target_core_cdb.c
+++ b/drivers/target/target_core_cdb.c
@@ -1115,9 +1115,10 @@ int target_emulate_unmap(struct se_task *task)
struct se_device *dev = cmd->se_dev;
unsigned char *buf, *ptr = NULL;
sector_t lba;
- unsigned int size = cmd->data_length, range;
- int ret = 0, offset;
- unsigned short dl, bd_dl;
+ int size = cmd->data_length;
+ u32 range;
+ int ret = 0;
+ int dl, bd_dl;
if (!dev->transport->do_discard) {
pr_err("UNMAP emulation not supported for: %s\n",
@@ -1126,20 +1127,19 @@ int target_emulate_unmap(struct se_task *task)
return -ENOSYS;
}
- /* First UNMAP block descriptor starts at 8 byte offset */
- offset = 8;
- size -= 8;
-
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",
--
1.7.7.6
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