tcmu: Fix possible to/from address overflow when doing the memcpy

For most case the sg->length equals to PAGE_SIZE, so this bug won't
be triggered. Otherwise this will crash the kernel, for example when
all segments' sg->length equal to 1K.

Signed-off-by: Xiubo Li <lixiubo@cmss.chinamobile.com>
Reviewed-by: Mike Christie <mchristi@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

diff --git a/drivers/target/target_core_user.c b/drivers/target/target_core_user.c
index 80ee130..db29b5c 100644 (file)
--- a/drivers/target/target_core_user.c
+++ b/drivers/target/target_core_user.c
@@ -563,8 +563,6 @@ static int scatter_data_area(struct tcmu_dev *udev,
                                        block_remaining);
                        to_offset = get_block_offset_user(udev, dbi,
                                        block_remaining);
-                       offset = DATA_BLOCK_SIZE - block_remaining;
-                       to += offset;
 
                        if (*iov_cnt != 0 &&
                            to_offset == iov_tail(*iov)) {
@@ -575,8 +573,10 @@ static int scatter_data_area(struct tcmu_dev *udev,
                                (*iov)->iov_len = copy_bytes;
                        }
                        if (copy_data) {
-                               memcpy(to, from + sg->length - sg_remaining,
-                                       copy_bytes);
+                               offset = DATA_BLOCK_SIZE - block_remaining;
+                               memcpy(to + offset,
+                                      from + sg->length - sg_remaining,
+                                      copy_bytes);
                                tcmu_flush_dcache_range(to, copy_bytes);
                        }
                        sg_remaining -= copy_bytes;
@@ -637,9 +637,8 @@ static void gather_data_area(struct tcmu_dev *udev, struct tcmu_cmd *cmd,
                        copy_bytes = min_t(size_t, sg_remaining,
                                        block_remaining);
                        offset = DATA_BLOCK_SIZE - block_remaining;
-                       from += offset;
                        tcmu_flush_dcache_range(from, copy_bytes);
-                       memcpy(to + sg->length - sg_remaining, from,
+                       memcpy(to + sg->length - sg_remaining, from + offset,
                                        copy_bytes);
 
                        sg_remaining -= copy_bytes;