Commit b704f70ce200 ("SCSI: fix bug in scsi_dev_info_list matching")
changed the way vendor- and model-string matching was carried out in
the routine that looks up entries in a SCSI devinfo list. The new
matching code failed to take into account the case of a maximum-length
string; in such cases it could end up testing for a terminating '\0'
byte beyond the end of the memory allocated to the string. This
out-of-bounds bug was detected by UBSAN.
I don't know if anybody has actually encountered this bug. The
symptom would be that a device entry in the blacklist might not be
matched properly if it contained an 8-character vendor name or a
16-character model name. Such entries certainly exist in
scsi_static_device_list.
This patch fixes the problem by adding a check for a maximum-length
string before the '\0' test.
Signed-off-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
Fixes: b704f70ce200 ("SCSI: fix bug in scsi_dev_info_list matching")
Tested-by: Wilfried Klaebe <linux-kernel@xxxxxxxxxxxxxxxxxxxxxxxxxx>
CC: <stable@xxxxxxxxxxxxxxx>
---
[as1804]
drivers/scsi/scsi_devinfo.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
Index: usb-4.x/drivers/scsi/scsi_devinfo.c
===================================================================
--- usb-4.x.orig/drivers/scsi/scsi_devinfo.c
+++ usb-4.x/drivers/scsi/scsi_devinfo.c
@@ -429,7 +429,7 @@ static struct scsi_dev_info_list *scsi_d
* here, and we don't know what device it is
* trying to work with, leave it as-is.
*/
- vmax = 8; /* max length of vendor */
+ vmax = sizeof(devinfo->vendor);
vskip = vendor;
while (vmax > 0 && *vskip == ' ') {
vmax--;
@@ -439,7 +439,7 @@ static struct scsi_dev_info_list *scsi_d
while (vmax > 0 && vskip[vmax - 1] == ' ')
--vmax;
- mmax = 16; /* max length of model */
+ mmax = sizeof(devinfo->model);
mskip = model;
while (mmax > 0 && *mskip == ' ') {
mmax--;
@@ -455,10 +455,12 @@ static struct scsi_dev_info_list *scsi_d
* Behave like the older version of get_device_flags.
*/
if (memcmp(devinfo->vendor, vskip, vmax) ||
- devinfo->vendor[vmax])
+ (vmax < sizeof(devinfo->vendor) &&
+ devinfo->vendor[vmax]))
continue;
if (memcmp(devinfo->model, mskip, mmax) ||
- devinfo->model[mmax])
+ (mmax < sizeof(devinfo->model) &&
+ devinfo->model[mmax]))
continue;
return devinfo;
} else {
--
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