[PATCH v2 08/21] libmultipath (coverity): fix tainted values in alua_rtpg.c

[mwilck@xxxxxxxx]

From: Martin Wilck <mwilck@xxxxxxxx>

Coverity needs tainted values limited by constant expressions.

Signed-off-by: Martin Wilck <mwilck@xxxxxxxx>
---
 libmultipath/prioritizers/alua_rtpg.c | 13 ++++----
 libmultipath/prioritizers/alua_spc3.h | 43 +++++++++++++++++++++++----
 2 files changed, 43 insertions(+), 13 deletions(-)

diff --git a/libmultipath/prioritizers/alua_rtpg.c b/libmultipath/prioritizers/alua_rtpg.c
index 420a2e3..3f9c0e7 100644
--- a/libmultipath/prioritizers/alua_rtpg.c
+++ b/libmultipath/prioritizers/alua_rtpg.c
@@ -27,7 +27,6 @@
 #include "../structs.h"
 #include "../prio.h"
 #include "../discovery.h"
-#include "../unaligned.h"
 #include "../debug.h"
 #include "alua_rtpg.h"
 
@@ -252,12 +251,12 @@ int
 get_target_port_group(const struct path * pp, unsigned int timeout)
 {
 	unsigned char		*buf;
-	struct vpd83_data *	vpd83;
-	struct vpd83_dscr *	dscr;
+	const struct vpd83_data *	vpd83;
+	const struct vpd83_dscr *	dscr;
 	int			rc;
 	int			buflen, scsi_buflen;
 
-	buflen = 4096;
+	buflen = VPD_BUFLEN;
 	buf = (unsigned char *)malloc(buflen);
 	if (!buf) {
 		PRINT_DEBUG("malloc failed: could not allocate"
@@ -298,13 +297,13 @@ get_target_port_group(const struct path * pp, unsigned int timeout)
 	rc = -RTPG_NO_TPG_IDENTIFIER;
 	FOR_EACH_VPD83_DSCR(vpd83, dscr) {
 		if (vpd83_dscr_istype(dscr, IDTYPE_TARGET_PORT_GROUP)) {
-			struct vpd83_tpg_dscr *p;
+			const struct vpd83_tpg_dscr *p;
 			if (rc != -RTPG_NO_TPG_IDENTIFIER) {
 				PRINT_DEBUG("get_target_port_group: more "
 					    "than one TPG identifier found!");
 				continue;
 			}
-			p  = (struct vpd83_tpg_dscr *)dscr->data;
+			p  = (const struct vpd83_tpg_dscr *)dscr->data;
 			rc = get_unaligned_be16(p->tpg);
 		}
 	}
@@ -377,7 +376,7 @@ get_asymmetric_access_state(const struct path *pp, unsigned int tpg,
 	uint64_t		scsi_buflen;
 	int fd = pp->fd;
 
-	buflen = 4096;
+	buflen = VPD_BUFLEN;
 	buf = (unsigned char *)malloc(buflen);
 	if (!buf) {
 		PRINT_DEBUG ("malloc failed: could not allocate"
diff --git a/libmultipath/prioritizers/alua_spc3.h b/libmultipath/prioritizers/alua_spc3.h
index 7ba2cf4..f0a4bc4 100644
--- a/libmultipath/prioritizers/alua_spc3.h
+++ b/libmultipath/prioritizers/alua_spc3.h
@@ -14,6 +14,7 @@
  */
 #ifndef __SPC3_H__
 #define __SPC3_H__
+#include "../unaligned.h"
 
 /*=============================================================================
  * Definitions to support the standard inquiry command as defined in SPC-3.
@@ -177,7 +178,7 @@ struct vpd83_dscr {
 } __attribute__((packed));
 
 static inline int
-vpd83_dscr_istype(struct vpd83_dscr *d, unsigned char type)
+vpd83_dscr_istype(const struct vpd83_dscr *d, unsigned char type)
 {
 	return ((d->b1 & 7) == type);
 }
@@ -190,6 +191,38 @@ struct vpd83_data {
 	struct vpd83_dscr	data[0];
 } __attribute__((packed));
 
+#define VPD_BUFLEN 4096
+
+/* Returns the max byte offset in the VPD page from the start of the page */
+static inline unsigned int vpd83_max_offs(const struct vpd83_data *p)
+{
+	uint16_t len = get_unaligned_be16(p->length) + 4;
+
+	return len <= VPD_BUFLEN ? len : VPD_BUFLEN;
+}
+
+static inline bool
+vpd83_descr_fits(const struct vpd83_dscr *d, const struct vpd83_data *p)
+{
+	ptrdiff_t max_offs = vpd83_max_offs(p);
+	ptrdiff_t offs = ((const char *)d - (const char *)p);
+
+	/* make sure we can read d->length */
+	if (offs < 0 || offs > max_offs - 4)
+		return false;
+
+	offs += d->length + 4;
+	return offs <= max_offs;
+}
+
+static inline const struct vpd83_dscr *
+vpd83_next_dscr(const struct vpd83_dscr *d, const struct vpd83_data *p)
+{
+	ptrdiff_t offs = ((const char *)d - (const char *)p) + d->length + 4;
+
+	return (const struct vpd83_dscr *)((const char *)p + offs);
+}
+
 /*-----------------------------------------------------------------------------
  * This macro should be used to walk through all identification descriptors
  * defined in the code page 0x83.
@@ -199,11 +232,9 @@ struct vpd83_data {
  */
 #define FOR_EACH_VPD83_DSCR(p, d) \
 		for( \
-			d = p->data; \
-			(((char *) d) - ((char *) p)) < \
-			get_unaligned_be16(p->length); \
-			d = (struct vpd83_dscr *) \
-				((char *) d + d->length + 4) \
+			d = p->data;		  \
+			vpd83_descr_fits(d, p);	  \
+			d = vpd83_next_dscr(d, p) \
 		)
 
 /*=============================================================================
-- 
2.33.1


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