Affected: Linux

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

slab: ensure slab->obj_exts is clear in a newly allocated slab page

ktest recently reported crashes while running several buffered io tests with __alloc_tagging_slab_alloc_hook() at the top of the crash call stack. The signature indicates an invalid address dereference with low bits of slab->obj_exts being set. The bits were outside of the range used by page_memcg_data_flags and objext_flags and hence were not masked out by slab_obj_exts() when obtaining the pointer stored in slab->obj_exts. The typical crash log looks like this:

00510 Unable to handle kernel NULL pointer dereference at virtual address 0000000000000010 00510 Mem abort info: 00510 ESR = 0x0000000096000045 00510 EC = 0x25: DABT (current EL), IL = 32 bits 00510 SET = 0, FnV = 0 00510 EA = 0, S1PTW = 0 00510 FSC = 0x05: level 1 translation fault 00510 Data abort info: 00510 ISV = 0, ISS = 0x00000045, ISS2 = 0x00000000 00510 CM = 0, WnR = 1, TnD = 0, TagAccess = 0 00510 GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 00510 user pgtable: 4k pages, 39-bit VAs, pgdp=0000000104175000 00510 [0000000000000010] pgd=0000000000000000, p4d=0000000000000000, pud=0000000000000000 00510 Internal error: Oops: 0000000096000045 [#1] SMP 00510 Modules linked in: 00510 CPU: 10 UID: 0 PID: 7692 Comm: cat Not tainted 6.15.0-rc1-ktest-g189e17946605 #19327 NONE 00510 Hardware name: linux,dummy-virt (DT) 00510 pstate: 20001005 (nzCv daif -PAN -UAO -TCO -…