SCSI: fix bug in scsi_dev_info_list matching (b704f70c) · Commits · 戴 / test

The "compatible" matching algorithm used for looking up old-style blacklist entries in a scsi_dev_info_list is buggy. The core of the algorithm looks like this: if (memcmp(devinfo->vendor, vendor, min(max, strlen(devinfo->vendor)))) /* not a match */ where max is the length of the device's vendor string after leading spaces have been removed but trailing spaces have not. Because of the min() computation, either entry could be a proper substring of the other and the code would still think that they match. In the case originally reported, the device's vendor and product strings were "Inateck " and " ". These matched against the following entry in the global device list: {"", "Scanner", "1.80", BLIST_NOLUN} because "" is a substring of "Inateck " and "" (the result of removing leading spaces from the device's product string) is a substring of "Scanner". The mistaken match prevented the system from scanning and finding the device's second Logical Unit. This patch fixes the problem by making two changes. First, the code for leading-space removal is hoisted out of the loop. (This means it will sometimes run unnecessarily, but since a large percentage of all lookups involve the "compatible" entries in global device list, this should be an overall improvement.) Second and more importantly, the patch removes trailing spaces and adds a check to verify that the two resulting strings are exactly the same length. This prevents matches where one entry is a proper substring of the other. Signed-off-by:

Alan Stern <stern@rowland.harvard.edu> Reported-by:

Giulio Bernardi <ugilio@gmail.com> Tested-by:

Giulio Bernardi <ugilio@gmail.com> Signed-off-by:

James Bottomley <JBottomley@Odin.com>

drivers/scsi/scsi_devinfo.c

+35 −34

Original line number	Diff line number	Diff line
		@@ -407,17 +407,14 @@ static struct scsi_dev_info_list scsi_dev_info_list_find(const char vendor,
		struct scsi_dev_info_list *devinfo;
		struct scsi_dev_info_list_table *devinfo_table =
		scsi_devinfo_lookup_by_key(key);
		size_t vmax, mmax;
		const char vskip, mskip;

		if (IS_ERR(devinfo_table))
		return (struct scsi_dev_info_list *) devinfo_table;

		list_for_each_entry(devinfo, &devinfo_table->scsi_dev_info_list,
		dev_info_list) {
		if (devinfo->compatible) {
		/*
		* Behave like the older version of get_device_flags.
		*/
		size_t max;
		/* Prepare for "compatible" matches */

		/*
		* XXX why skip leading spaces? If an odd INQUIRY
		* value, that should have been part of the
		@@ -426,32 +423,36 @@ 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.
		*/
		max = 8; /* max length of vendor */
		while ((max > 0) && *vendor == ' ') {
		max--;
		vendor++;
		vmax = 8; /* max length of vendor */
		vskip = vendor;
		while (vmax > 0 && *vskip == ' ') {
		vmax--;
		vskip++;
		}
		/* Also skip trailing spaces */
		while (vmax > 0 && vskip[vmax - 1] == ' ')
		--vmax;

		mmax = 16; /* max length of model */
		mskip = model;
		while (mmax > 0 && *mskip == ' ') {
		mmax--;
		mskip++;
		}
		while (mmax > 0 && mskip[mmax - 1] == ' ')
		--mmax;

		list_for_each_entry(devinfo, &devinfo_table->scsi_dev_info_list,
		dev_info_list) {
		if (devinfo->compatible) {
		/*
		* XXX removing the following strlen() would be
		* good, using it means that for a an entry not in
		* the list, we scan every byte of every vendor
		* listed in scsi_static_device_list[], and never match
		* a single one (and still have to compare at
		* least the first byte of each vendor).
		* Behave like the older version of get_device_flags.
		*/
		if (memcmp(devinfo->vendor, vendor,
		min(max, strlen(devinfo->vendor))))
		if (memcmp(devinfo->vendor, vskip, vmax) \|\|
		devinfo->vendor[vmax])
		continue;
		/*
		* Skip spaces again.
		*/
		max = 16; /* max length of model */
		while ((max > 0) && *model == ' ') {
		max--;
		model++;
		}
		if (memcmp(devinfo->model, model,
		min(max, strlen(devinfo->model))))
		if (memcmp(devinfo->model, mskip, mmax) \|\|
		devinfo->model[mmax])
		continue;
		return devinfo;
		} else {

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