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selinux: reject a permission value exceeding the class permission count

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perm_read() bounds a permission value by SEL_VEC_MAX but never by the
nprim of the owning class or common, which is taken verbatim from the
policy image.  security_get_permissions() then writes perms[value - 1]
into an nprim-sized kcalloc() array, so a class declaring fewer
permissions than its largest permission value drives an out-of-bounds
heap write.  The top-level symbol tables are validated this way; the
nested per-class permission table is not.

Reject a permission whose value exceeds nprim, which is already set when
perm_read() runs.  Well-formed policies are unaffected.

Cc: stable@vger.kernel.org
Fixes: 55fcf09b3f ("selinux: add support for querying object classes and permissions from the running policy")
Signed-off-by: Bryam Vargas <hexlabsecurity@proton.me>
Acked-by: Stephen Smalley <stephen.smalley.work@gmail.com>
[PM: tweak comment for line length]
Signed-off-by: Paul Moore <paul@paul-moore.com>
This commit is contained in:
Bryam Vargas
2026-07-30 16:14:50 -04:00
committed by Paul Moore
parent f5098b6bae
commit d14b5d0e97
1 changed files with 3 additions and 0 deletions
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security/selinux/ss/policydb.c
+3
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@@ -1175,6 +1175,9 @@ static int perm_read(struct policydb *p, struct symtab *s, struct policy_file *f
rc = -EINVAL;
if (perdatum->value < 1 || perdatum->value > SEL_VEC_MAX)
goto bad;
/* indexes an nprim-sized array in security_get_permissions() */
if (perdatum->value > s->nprim)
goto bad;
rc = str_read(&key, GFP_KERNEL, fp, len);
if (rc)