topjohnwu/selinux
1
0
Fork 0
mirror of https://github.com/topjohnwu/selinux.git synced 2024-12-11 13:26:01 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

libsepol/cil: fix bug when resetting class permission values

Browse Source 
During resolution of classcommon statements (cil_resolve_classcommon),
we add the number of class common permissions to the values of the class
permissions. This way, the internal CIL values of the common permission
go from 0 to N, and the values of class permissions start at N+1 (where
N is the number of common permissions). When we reset a class due to
reresolve (cil_reset_class), we must then reverse this process by
subtracting the number of common permissions from the class permission
values.

However, there is a bug when resetting classes in which we subtract the
number of common permissions from the common permissions value rather
than the class permissions value. This means that class permissions
could be too high (since they are not reduced on reset) and common
permissions underflowed (since they are reduced, but should not be).

In most cases, this didn't actually matter since these permission values
aren't used when creating the binary. Additionally, we always access the
permissions via a hash table lookup or map, and then use whatever value
they have to set bits in bitmaps. As long as the bits in the bitmap
match the values, things work as expected. However, the one case where
these values do matter is if you use 'all' in a class permission set. In
this case, we enable bits 0 through number of permissions in a bitmap.
But because our permission values are all mixed up, these enabled bits
do not correspond to the permission values. This results in making it
look like no permissions were set in a class permission set, and the
rule is essentially ignored.

This patch fixes the bug so that the values of class permissions are
properly reset, allowing one to use 'all' in class permission sets in a
policy that reresolves.

Signed-off-by: Steve Lawrence <slawrence@tresys.com>
Signed-off-by: James Carter <jwcart2@tycho.nsa.gov>
This commit is contained in:
Steve Lawrence 2016-03-17 15:29:51 -04:00 committed by James Carter
parent 58dcbcd0db
commit 4df9f89cb1
1 changed files with 1 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
libsepol/cil/src/cil_reset_ast.c
View File

@ -23,7 +23,7 @@ static void cil_reset_class(struct cil_class *class)
{
if (class->common != NULL) {
struct cil_class *common = class->common;
cil_symtab_map(&common->perms, __class_reset_perm_values, &common->num_perms);
cil_symtab_map(&class->perms, __class_reset_perm_values, &common->num_perms);
/* during a re-resolve, we need to reset the common, so a classcommon
* statement isn't seen as a duplicate */
class->num_perms -= common->num_perms;