2023-08-07 19:01:53

by Christian Göttsche

Subject: [PATCH v3 4/7] selinux: make left shifts well defined

The loops upper bound represent the number of permissions used (for the
current class or in general). The limit for this is 32, thus we might
left shift of one less, 31. Shifting a base of 1 results in undefined
behavior; use (u32)1 as base.

Signed-off-by: Christian Göttsche <[email protected]>
---
v3: split from parent commit and apply cast to correct shift operand
---
security/selinux/ss/services.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
index dacec2ebdcd7..1eeffc66ea7d 100644
--- a/security/selinux/ss/services.c
+++ b/security/selinux/ss/services.c
@@ -207,22 +207,22 @@ static void map_decision(struct selinux_map *map,

for (i = 0, result = 0; i < n; i++) {
if (avd->allowed & mapping->perms[i])
- result |= 1<<i;
+ result |= (u32)1<<i;
if (allow_unknown && !mapping->perms[i])
- result |= 1<<i;
+ result |= (u32)1<<i;
}
avd->allowed = result;

for (i = 0, result = 0; i < n; i++)
if (avd->auditallow & mapping->perms[i])
- result |= 1<<i;
+ result |= (u32)1<<i;
avd->auditallow = result;

for (i = 0, result = 0; i < n; i++) {
if (avd->auditdeny & mapping->perms[i])
- result |= 1<<i;
+ result |= (u32)1<<i;
if (!allow_unknown && !mapping->perms[i])
- result |= 1<<i;
+ result |= (u32)1<<i;
}
/*
* In case the kernel has a bug and requests a permission
@@ -230,7 +230,7 @@ static void map_decision(struct selinux_map *map,
* should audit that denial
*/
for (; i < (sizeof(u32)*8); i++)
- result |= 1<<i;
+ result |= (u32)1<<i;
avd->auditdeny = result;
}
}
--
2.40.1

2023-08-10 00:39:15

by Paul Moore

Subject: Re: [PATCH v3 4/7] selinux: make left shifts well defined

On Aug 7, 2023 =?UTF-8?q?Christian=20G=C3=B6ttsche?= <[email protected]> wrote:
>
> The loops upper bound represent the number of permissions used (for the
> current class or in general). The limit for this is 32, thus we might
> left shift of one less, 31. Shifting a base of 1 results in undefined
> behavior; use (u32)1 as base.
>
> Signed-off-by: Christian Göttsche <[email protected]>
> ---
> v3: split from parent commit and apply cast to correct shift operand
> ---
> security/selinux/ss/services.c | 12 ++++++------
> 1 file changed, 6 insertions(+), 6 deletions(-)

Merged into selinux/next, thanks.

--
paul-moore.com