AZL-93713

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

partitions: aix: bound the pp_count scan to the ppe array

aix_partition() reads the physical volume descriptor into a fixed-size struct pvd and then scans its physical-partition-extent array:

int numpps = be16_to_cpu(pvd->pp_count);
...
for (i = 0; i < numpps; i += 1) {
    struct ppe *p = pvd->ppe + i;
    ...
    lp_ix = be16_to_cpu(p->lp_ix);

pvd points at a single kmalloc()'d struct pvd whose ppe[] member holds a fixed ARRAYSIZE(pvd->ppe) (1016) entries, but the loop runs up to the on-disk ppcount. pp_count is an unvalidated _be16 read straight from the descriptor, so a crafted AIX image with ppcount larger than 1016 drives the loop to read pvd->ppe[i] past the end of the allocation (up to 65535 entries, ~2 MB out of bounds).

The partition scan runs without mounting anything, when a block device with a crafted AIX/IBM partition table appears (an attacker-supplied image attached with losetup -P, or a device auto-scanned by udev), via msdospartition() -> aixpartition().

Clamp the scan to the number of entries the ppe[] array can hold.