From: Michal Hocko <mhocko@xxxxxxxx> Subject: mm, slab: make sure that KMALLOC_MAX_SIZE will fit into MAX_ORDER Andrey Konovalov has reported the following warning triggered by the syzkaller fuzzer. WARNING: CPU: 1 PID: 9935 at mm/page_alloc.c:3511 __alloc_pages_nodemask+0x159c/0x1e20 Kernel panic - not syncing: panic_on_warn set ... CPU: 1 PID: 9935 Comm: syz-executor0 Not tainted 4.9.0-rc7+ #34 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 ffff88006949f2c8 ffffffff81f96b8a ffffffff00000200 1ffff1000d293dec ffffed000d293de4 0000000000000a06 0000000041b58ab3 ffffffff8598b510 ffffffff81f968f8 0000000041b58ab3 ffffffff85942a58 ffffffff81432860 Call Trace: [< inline >] __dump_stack lib/dump_stack.c:15 [<ffffffff81f96b8a>] dump_stack+0x292/0x398 lib/dump_stack.c:51 [<ffffffff8168c88e>] panic+0x1cb/0x3a9 kernel/panic.c:179 [<ffffffff812b80b4>] __warn+0x1c4/0x1e0 kernel/panic.c:542 [<ffffffff812b831c>] warn_slowpath_null+0x2c/0x40 kernel/panic.c:585 [< inline >] __alloc_pages_slowpath mm/page_alloc.c:3511 [<ffffffff816c08ac>] __alloc_pages_nodemask+0x159c/0x1e20 mm/page_alloc.c:3781 [<ffffffff817cde17>] alloc_pages_current+0x1c7/0x6b0 mm/mempolicy.c:2072 [< inline >] alloc_pages include/linux/gfp.h:469 [<ffffffff8172fd8f>] kmalloc_order+0x1f/0x70 mm/slab_common.c:1015 [<ffffffff8172fdff>] kmalloc_order_trace+0x1f/0x160 mm/slab_common.c:1026 [< inline >] kmalloc_large include/linux/slab.h:422 [<ffffffff817e01f0>] __kmalloc+0x210/0x2d0 mm/slub.c:3723 [< inline >] kmalloc include/linux/slab.h:495 [<ffffffff832262a7>] ep_write_iter+0x167/0xb50 drivers/usb/gadget/legacy/inode.c:664 [< inline >] new_sync_write fs/read_write.c:499 [<ffffffff817fdcd3>] __vfs_write+0x483/0x760 fs/read_write.c:512 [<ffffffff817ff720>] vfs_write+0x170/0x4e0 fs/read_write.c:560 [< inline >] SYSC_write fs/read_write.c:607 [<ffffffff81803b2b>] SyS_write+0xfb/0x230 fs/read_write.c:599 [<ffffffff84f47ec1>] entry_SYSCALL_64_fastpath+0x1f/0xc2 The issue is caused by a lack of size check for the request size in ep_write_iter which should be fixed. It, however, points to another problem, that SLUB defines KMALLOC_MAX_SIZE too large because the its KMALLOC_SHIFT_MAX is (MAX_ORDER + PAGE_SHIFT) which means that the resulting page allocator request might be MAX_ORDER which is too large (see __alloc_pages_slowpath). The same applies to the SLOB allocator which allows even larger sizes. Make sure that they are capped properly and never request more than MAX_ORDER order. Link: http://lkml.kernel.org/r/20161220130659.16461-2-mhocko@xxxxxxxxxx Signed-off-by: Michal Hocko <mhocko@xxxxxxxx> Reported-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx> Acked-by: Christoph Lameter <cl@xxxxxxxxx> Cc: Alexei Starovoitov <ast@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/slab.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff -puN include/linux/slab.h~mm-slab-make-sure-that-kmalloc_max_size-will-fit-into-max_order include/linux/slab.h --- a/include/linux/slab.h~mm-slab-make-sure-that-kmalloc_max_size-will-fit-into-max_order +++ a/include/linux/slab.h @@ -226,7 +226,7 @@ static inline const char *__check_heap_o * (PAGE_SIZE*2). Larger requests are passed to the page allocator. */ #define KMALLOC_SHIFT_HIGH (PAGE_SHIFT + 1) -#define KMALLOC_SHIFT_MAX (MAX_ORDER + PAGE_SHIFT) +#define KMALLOC_SHIFT_MAX (MAX_ORDER + PAGE_SHIFT - 1) #ifndef KMALLOC_SHIFT_LOW #define KMALLOC_SHIFT_LOW 3 #endif @@ -239,7 +239,7 @@ static inline const char *__check_heap_o * be allocated from the same page. */ #define KMALLOC_SHIFT_HIGH PAGE_SHIFT -#define KMALLOC_SHIFT_MAX 30 +#define KMALLOC_SHIFT_MAX (MAX_ORDER + PAGE_SHIFT - 1) #ifndef KMALLOC_SHIFT_LOW #define KMALLOC_SHIFT_LOW 3 #endif _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
