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Subjectuser-controllable kmalloc size in bpf syscall
Hello,

The following program triggers a WARNING in kmalloc:

// autogenerated by syzkaller (http://github.com/google/syzkaller)
#include <syscall.h>
#include <string.h>
#include <stdint.h>

#define SYS_bpf 321
#define BPF_MAP_CREATE 0
#define BPF_MAP_UPDATE_ELEM 2

union bpf_attr {
struct {
uint32_t map_type; /* one of enum bpf_map_type */
uint32_t key_size; /* size of key in bytes */
uint32_t value_size; /* size of value in bytes */
uint32_t max_entries; /* max number of
entries in a map */
};

struct {
uint32_t map_fd;
uint64_t key;
uint64_t val;
uint64_t flags;
};
};

int main()
{
union bpf_attr ca;
memset(&ca, 0, sizeof(ca));
ca.map_type = 1;
ca.key_size = 1;
ca.value_size = 0xfffffff9;
ca.max_entries = 10;
int fd = syscall(SYS_bpf, BPF_MAP_CREATE, &ca, sizeof(ca));
memset(&ca, 0, sizeof(ca));
ca.map_fd = fd;
ca.key = &ca;
ca.val = &ca;
ca.flags = 0;
syscall(SYS_bpf, BPF_MAP_UPDATE_ELEM, &ca, sizeof(ca));
return 0;
}


------------[ cut here ]------------
WARNING: CPU: 2 PID: 11122 at mm/page_alloc.c:2989
__alloc_pages_nodemask+0x695/0x14e0()
Modules linked in:
CPU: 2 PID: 11122 Comm: syzkaller_execu Tainted: G B 4.4.0-rc2+ #5
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
00000000ffffffff ffff880039aefa30 ffffffff82743b56 0000000000000000
ffff88003b2a0000 ffffffff85a8d0e0 ffff880039aefa70 ffffffff81244ec9
ffffffff81554e95 ffffffff85a8d0e0 0000000000000bad 0000000000000000
Call Trace:
[< inline >] __dump_stack lib/dump_stack.c:15
[<ffffffff82743b56>] dump_stack+0x68/0x92 lib/dump_stack.c:50
[<ffffffff81244ec9>] warn_slowpath_common+0xd9/0x140 kernel/panic.c:460
[<ffffffff812450f9>] warn_slowpath_null+0x29/0x30 kernel/panic.c:493
[< inline >] __alloc_pages_slowpath mm/page_alloc.c:2989
[<ffffffff81554e95>] __alloc_pages_nodemask+0x695/0x14e0 mm/page_alloc.c:3235
[<ffffffff816188fe>] alloc_pages_current+0xee/0x340 mm/mempolicy.c:2055
[< inline >] alloc_pages include/linux/gfp.h:451
[<ffffffff81550706>] alloc_kmem_pages+0x16/0xf0 mm/page_alloc.c:3414
[<ffffffff815a1c89>] kmalloc_order+0x19/0x60 mm/slab_common.c:1007
[<ffffffff815a1cef>] kmalloc_order_trace+0x1f/0xa0 mm/slab_common.c:1018
[< inline >] kmalloc_large include/linux/slab.h:390
[<ffffffff81627784>] __kmalloc+0x234/0x250 mm/slub.c:3525
[< inline >] kmalloc include/linux/slab.h:463
[< inline >] map_update_elem kernel/bpf/syscall.c:288
[< inline >] SYSC_bpf kernel/bpf/syscall.c:744
[<ffffffff814f07c4>] SyS_bpf+0xfd4/0x1a20 kernel/bpf/syscall.c:695
[<ffffffff8597eeb6>] entry_SYSCALL_64_fastpath+0x16/0x7a
arch/x86/entry/entry_64.S:185
---[ end trace f00640b4d448df95 ]---


On commit 78c4a49a69e910a162b05e4e8727b9bdbf948f13 (Now 25).


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