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authorJonathan Brassow <jbrassow@redhat.com>2010-02-16 18:42:53 +0000
committerGreg Kroah-Hartman <gregkh@suse.de>2010-02-23 07:37:58 -0800
commitc7f14122d1c633d5d6d9c999235d7f6778510b26 (patch)
tree024ef22b9203030c48899cecd19d4247961d07ef
parent7607864c43f7d2559153179fabd9dc8ade6b70a0 (diff)
dm log: userspace fix overhead_size calcuations
commit ebfd32bba9b518d684009d9d21a56742337ca1b3 upstream. This patch fixes two bugs that revolve around the miscalculation and misuse of the variable 'overhead_size'. 'overhead_size' is the size of the various header structures used during communication. The first bug is the use of 'sizeof' with the pointer of a structure instead of the structure itself - resulting in the wrong size being computed. This is then used in a check to see if the payload (data_size) would be to large for the preallocated structure. Since the bug produces a smaller value for the overhead, it was possible for the structure to be breached. (Although the current users of the code do not currently send enough data to trigger this bug.) The second bug is that the 'overhead_size' value is used to compute how much of the preallocated space should be cleared before populating it with fresh data. This should have simply been 'sizeof(struct cn_msg)' not overhead_size. The fact that 'overhead_size' was computed incorrectly made this problem "less bad" - leaving only a pointer's worth of space at the end uncleared. Thus, this bug was never producing a bad result, but still needs to be fixed - especially now that the value is computed correctly. Signed-off-by: Jonathan Brassow <jbrassow@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r--drivers/md/dm-log-userspace-transfer.c10
1 files changed, 7 insertions, 3 deletions
diff --git a/drivers/md/dm-log-userspace-transfer.c b/drivers/md/dm-log-userspace-transfer.c
index 54abf9e303b7..f1c8cae70b4b 100644
--- a/drivers/md/dm-log-userspace-transfer.c
+++ b/drivers/md/dm-log-userspace-transfer.c
@@ -172,11 +172,15 @@ int dm_consult_userspace(const char *uuid, uint64_t luid, int request_type,
{
int r = 0;
size_t dummy = 0;
- int overhead_size =
- sizeof(struct dm_ulog_request *) + sizeof(struct cn_msg);
+ int overhead_size = sizeof(struct dm_ulog_request) + sizeof(struct cn_msg);
struct dm_ulog_request *tfr = prealloced_ulog_tfr;
struct receiving_pkg pkg;
+ /*
+ * Given the space needed to hold the 'struct cn_msg' and
+ * 'struct dm_ulog_request' - do we have enough payload
+ * space remaining?
+ */
if (data_size > (DM_ULOG_PREALLOCED_SIZE - overhead_size)) {
DMINFO("Size of tfr exceeds preallocated size");
return -EINVAL;
@@ -191,7 +195,7 @@ resend:
*/
mutex_lock(&dm_ulog_lock);
- memset(tfr, 0, DM_ULOG_PREALLOCED_SIZE - overhead_size);
+ memset(tfr, 0, DM_ULOG_PREALLOCED_SIZE - sizeof(struct cn_msg));
memcpy(tfr->uuid, uuid, DM_UUID_LEN);
tfr->luid = luid;
tfr->seq = dm_ulog_seq++;