Re: [Non-DoD Source] [PATCH 1/1] libsepol: do not use uninitialized value for low_value

[jwcart2 <jwcart2@xxxxxxxxxxxxx>]

On 2/3/19 6:01 AM, Nicolas Iooss wrote:
> clang's static analyzer reports a warning when low_bit is used without
> having been initialized in statements such as:
>
>      low_value = low_bit << 8;
>
> The warning is: "Result of operation is garbage or undefined".
>
> This is caused by low_bit being only initialized when in_range is true.
> This issue is not critical because low_value is only used in an
> "if (in_range)" block. Silence this warning by moving low_value's
> assignment inside this block.
>
> Signed-off-by: Nicolas Iooss <nicolas.iooss@xxxxxxx>

Acked-by: James Carter <jwcart2@xxxxxxxxxxxxx>

> ---
>   libsepol/src/kernel_to_cil.c | 4 ++--
>   libsepol/src/module_to_cil.c | 4 ++--
>   libsepol/src/util.c          | 4 ++--
>   3 files changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/libsepol/src/kernel_to_cil.c b/libsepol/src/kernel_to_cil.c
> index 63e4d4899758..cd3554e8dfd9 100644
> --- a/libsepol/src/kernel_to_cil.c
> +++ b/libsepol/src/kernel_to_cil.c
> @@ -1614,8 +1614,8 @@ static char *xperms_to_str(avtab_extended_perms_t *xperms)
>   
>   		if (xperms->specified & AVTAB_XPERMS_IOCTLFUNCTION) {
>   			value = xperms->driver<<8 | bit;
> -			low_value = xperms->driver<<8 | low_bit;
>   			if (in_range) {
> +				low_value = xperms->driver<<8 | low_bit;
>   				len = snprintf(p, remaining, " (range 0x%hx 0x%hx)", low_value, value);
>   				in_range = 0;
>   			} else {
> @@ -1623,8 +1623,8 @@ static char *xperms_to_str(avtab_extended_perms_t *xperms)
>   			}
>   		} else if (xperms->specified & AVTAB_XPERMS_IOCTLDRIVER) {
>   			value = bit << 8;
> -			low_value = low_bit << 8;
>   			if (in_range) {
> +				low_value = low_bit << 8;
>   				len = snprintf(p, remaining, " (range 0x%hx 0x%hx)", low_value, (uint16_t) (value|0xff));
>   				in_range = 0;
>   			} else {
> diff --git a/libsepol/src/module_to_cil.c b/libsepol/src/module_to_cil.c
> index 4cb44e0ee657..f04589edaeff 100644
> --- a/libsepol/src/module_to_cil.c
> +++ b/libsepol/src/module_to_cil.c
> @@ -655,8 +655,8 @@ static int xperms_to_cil(const av_extended_perms_t *xperms)
>   
>   		if (xperms->specified & AVTAB_XPERMS_IOCTLFUNCTION) {
>   			value = xperms->driver<<8 | bit;
> -			low_value = xperms->driver<<8 | low_bit;
>   			if (in_range) {
> +				low_value = xperms->driver<<8 | low_bit;
>   				cil_printf("(range 0x%hx 0x%hx)", low_value, value);
>   				in_range = 0;
>   			} else {
> @@ -664,8 +664,8 @@ static int xperms_to_cil(const av_extended_perms_t *xperms)
>   			}
>   		} else if (xperms->specified & AVTAB_XPERMS_IOCTLDRIVER) {
>   			value = bit << 8;
> -			low_value = low_bit << 8;
>   			if (in_range) {
> +				low_value = low_bit << 8;
>   				cil_printf("(range 0x%hx 0x%hx)", low_value, (uint16_t) (value|0xff));
>   				in_range = 0;
>   			} else {
> diff --git a/libsepol/src/util.c b/libsepol/src/util.c
> index b00251c69aa5..a4008882b94b 100644
> --- a/libsepol/src/util.c
> +++ b/libsepol/src/util.c
> @@ -159,16 +159,16 @@ char *sepol_extended_perms_to_string(avtab_extended_perms_t *xperms)
>   
>   		if (xperms->specified & AVTAB_XPERMS_IOCTLFUNCTION) {
>   			value = xperms->driver<<8 | bit;
> -			low_value = xperms->driver<<8 | low_bit;
>   			if (in_range) {
> +				low_value = xperms->driver<<8 | low_bit;
>   				len = snprintf(p, sizeof(xpermsbuf) - xpermslen, "0x%hx-0x%hx ", low_value, value);
>   			} else {
>   				len = snprintf(p, sizeof(xpermsbuf) - xpermslen, "0x%hx ", value);
>   			}
>   		} else if (xperms->specified & AVTAB_XPERMS_IOCTLDRIVER) {
>   			value = bit << 8;
> -			low_value = low_bit << 8;
>   			if (in_range) {
> +				low_value = low_bit << 8;
>   				len = snprintf(p, sizeof(xpermsbuf) - xpermslen, "0x%hx-0x%hx ", low_value, (uint16_t) (value|0xff));
>   			} else {
>   				len = snprintf(p, sizeof(xpermsbuf) - xpermslen, "0x%hx-0x%hx ", value, (uint16_t) (value|0xff));


--
James Carter <jwcart2@xxxxxxxxxxxxx>
National Security Agency