CVE-2026-90246: apparmor: fix integer overflow in verify_tags() bounds check

In the Linux kernel, the following vulnerability has been resolved:

apparmor: fix integer overflow in verifytags() bounds check

verifytags() validates the tagset table unpacked from a policy blob. For each set it reads a count and checks that advancing the index by that count stays inside sets.table[]:

u32 cnt = tags->sets.table[i];

if (i+cnt >= tags->sets.size) {

i, cnt and sets.size are all u32, so i+cnt is evaluated modulo 2^32. sets.table[] is filled by unpacktagsets() with aaunpacku32(), so every entry is a raw unbounded 32-bit word taken from the policy blob, and verifytags() is the function that is supposed to validate it. A count close to U32MAX makes the sum wrap to a small value, the guard passes, and the inner loop then walks sets.table[++i] past the end of the kcalloc(size, sizeof(u32)) allocation.

Note that sets.size is bounded by 65535, because unpacktagsets() reads it with aaunpackarray() as a u16, so the wrap cannot be reached by growing the table; it is reached purely through the attacker-supplied count.

With sets.size = 2 and sets.table = { 0, 0xffffffff }:

i = 0: cnt = 0, guard 0 + 0 >= 2 is false, inner loop does not run i = 1: cnt = 0xffffffff, guard (1 + 0xffffffff) mod 2^32 == 0 >= 2 is false, so the guard is bypassed and the inner loop reads sets.table[2] -- one element past a two element allocation

The walk continues until an out-of-bounds value happens to be >= hdrs.size or the access faults, so a crafted policy yields an out-of-bounds read on the policy load path (aareplaceprofiles -> aaunpack -> unpackpolicydb -> unpacktags -> verifytags). unpacktags() runs before the perms and DFA tables are unpacked, so no other table needs to be well formed to reach it.

Policy load is gated by aamaymanagepolicy(), which checks CAPMACADMIN relative to the subject's own user namespace rather than the init user namespace, so with the default unprivilegedusernsapparmorpolicy=1 the path is reachable from an unprivileged task in a matched-level nested namespace, not only by a globally privileged one.

Perform the addition in u64 so that it cannot wrap, restoring the intended i + cnt < sets.size guarantee.