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SubjectRe: UBSAN: Undefined behaviour in mm/page_alloc.c
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On 11/9/18 5:09 AM, Kyungtae Kim wrote:
> We report a bug in v4.19-rc2 (4.20-rc1 as well, I guess):
>
> kernel config: https://kt0755.github.io/etc/config_v2-4.19
> repro: https://kt0755.github.io/etc/repro.c4074.c
>
> In the middle of page request, this arose because order is too large to handle
> (mm/page_alloc.c:3119). It actually comes from that order is
> controllable by user input
> via raw_cmd_ioctl without its sanity check, thereby causing memory problem.
> To stop it, we can use like MAX_ORDER for bounds check before using it.

This together with [1] makes me rather convinced that we should really
move the check back from __alloc_pages_slowpath to
__alloc_pages_nodemask. It should be a single predictable branch with an
unlikely()?

[1]
https://lore.kernel.org/lkml/154109387197.925352.10499549042420271600.stgit@buzz/T/#u

> =========================================
> UBSAN: Undefined behaviour in mm/page_alloc.c:3117:19
> shift exponent 51 is too large for 32-bit type 'int'
> CPU: 0 PID: 6520 Comm: syz-executor1 Not tainted 4.19.0-rc2 #1
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
> Call Trace:
> __dump_stack lib/dump_stack.c:77 [inline]
> dump_stack+0xd2/0x148 lib/dump_stack.c:113
> ubsan_epilogue+0x12/0x94 lib/ubsan.c:159
> __ubsan_handle_shift_out_of_bounds+0x2b6/0x30b lib/ubsan.c:425
> __zone_watermark_ok+0x2c7/0x400 mm/page_alloc.c:3117
> zone_watermark_fast mm/page_alloc.c:3216 [inline]
> get_page_from_freelist+0xc49/0x44c0 mm/page_alloc.c:3300
> __alloc_pages_nodemask+0x21e/0x640 mm/page_alloc.c:4370
> alloc_pages_current+0xcc/0x210 mm/mempolicy.c:2093
> alloc_pages include/linux/gfp.h:509 [inline]
> __get_free_pages+0x12/0x60 mm/page_alloc.c:4414
> dma_mem_alloc+0x36/0x50 arch/x86/include/asm/floppy.h:156
> raw_cmd_copyin drivers/block/floppy.c:3159 [inline]
> raw_cmd_ioctl drivers/block/floppy.c:3206 [inline]
> fd_locked_ioctl+0xa00/0x2c10 drivers/block/floppy.c:3544
> fd_ioctl+0x40/0x60 drivers/block/floppy.c:3571
> __blkdev_driver_ioctl block/ioctl.c:303 [inline]
> blkdev_ioctl+0xb3c/0x1a30 block/ioctl.c:601
> block_ioctl+0x105/0x150 fs/block_dev.c:1883
> vfs_ioctl fs/ioctl.c:46 [inline]
> do_vfs_ioctl+0x1c0/0x1150 fs/ioctl.c:687
> ksys_ioctl+0x9e/0xb0 fs/ioctl.c:702
> __do_sys_ioctl fs/ioctl.c:709 [inline]
> __se_sys_ioctl fs/ioctl.c:707 [inline]
> __x64_sys_ioctl+0x7e/0xc0 fs/ioctl.c:707
> do_syscall_64+0xc4/0x510 arch/x86/entry/common.c:290
> entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x4497b9
> Code: e8 8c 9f 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 00 48 89 f8 48
> 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d
> 01 f0 ff ff 0f 83 9b 6b fc ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007fb5ef0e2c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> RAX: ffffffffffffffda RBX: 00007fb5ef0e36cc RCX: 00000000004497b9
> RDX: 0000000020000040 RSI: 0000000000000258 RDI: 0000000000000014
> RBP: 000000000071bea0 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
> R13: 0000000000005490 R14: 00000000006ed530 R15: 00007fb5ef0e3700
> =========================================================
>
>
> Thanks,
> Kyungtae Kim
>

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