Commit 5e7ff2ca authored Jun 23, 2016 by Alan Stern Committed by Martin K. Petersen Jun 29, 2016

SCSI: fix new bug in scsi_dev_info_list string matching



Commit b704f70c ("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@rowland.harvard.edu>
Fixes: b704f70c ("SCSI: fix bug in scsi_dev_info_list matching")
Tested-by: Wilfried Klaebe <linux-kernel@lebenslange-mailadresse.de>
CC: <stable@vger.kernel.org> # v4.4+
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

parent 54e430bb

drivers/scsi/scsi_devinfo.c

+6 −4

Original line number	Diff line number	Diff line
		@@ -429,7 +429,7 @@ static struct scsi_dev_info_list scsi_dev_info_list_find(const char vendor,
		* 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_dev_info_list_find(const char vendor,
		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_dev_info_list_find(const char vendor,
		* 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 {