From: Alexander Potapenko <glider@xxxxxxxxxx> Subject: lib/stackdepot.c: fix global out-of-bounds in stack_slabs Walter Wu has reported a potential case in which init_stack_slab() is called after stack_slabs[STACK_ALLOC_MAX_SLABS - 1] has already been initialized. In that case init_stack_slab() will overwrite stack_slabs[STACK_ALLOC_MAX_SLABS], which may result in a memory corruption. Link: http://lkml.kernel.org/r/20200218102950.260263-1-glider@xxxxxxxxxx Fixes: cd11016e5f521 ("mm, kasan: stackdepot implementation. Enable stackdepot for SLAB") Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx> Reported-by: Walter Wu <walter-zh.wu@xxxxxxxxxxxx> Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Cc: Matthias Brugger <matthias.bgg@xxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> Cc: Kate Stewart <kstewart@xxxxxxxxxxxxxxxxxxx> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- lib/stackdepot.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) --- a/lib/stackdepot.c~lib-stackdepot-fix-global-out-of-bounds-in-stack_slabs +++ a/lib/stackdepot.c @@ -83,15 +83,19 @@ static bool init_stack_slab(void **preal return true; if (stack_slabs[depot_index] == NULL) { stack_slabs[depot_index] = *prealloc; + *prealloc = NULL; } else { - stack_slabs[depot_index + 1] = *prealloc; + /* If this is the last depot slab, do not touch the next one. */ + if (depot_index + 1 < STACK_ALLOC_MAX_SLABS) { + stack_slabs[depot_index + 1] = *prealloc; + *prealloc = NULL; + } /* * This smp_store_release pairs with smp_load_acquire() from * |next_slab_inited| above and in stack_depot_save(). */ smp_store_release(&next_slab_inited, 1); } - *prealloc = NULL; return true; } _
