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

[Benjamin Marzinski <bmarzins@redhat.com>]

On Wed, Dec 01, 2021 at 01:36:37PM +0100, mwilck@suse.com wrote:
> From: Martin Wilck <mwilck@suse.com>
> 
> Coverity needs tainted values limited by constant expressions.
> 
> Signed-off-by: Martin Wilck <mwilck@suse.com>
Reviewed-by: Benjamin Marzinski <bmarzins@redhat.com>
> ---
>  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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