Re: KASAN: slab-out-of-bounds Read in p54u_load_firmware_cb

[Alan Stern]

On Wed, 19 Jun 2019, syzbot wrote:

> syzbot has found a reproducer for the following crash on:
> 
> HEAD commit:    9939f56e usb-fuzzer: main usb gadget fuzzer driver
> git tree:       https://github.com/google/kasan.git usb-fuzzer
> console output: https://syzkaller.appspot.com/x/log.txt?x=135e29faa00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=df134eda130bb43a
> dashboard link: https://syzkaller.appspot.com/bug?extid=6d237e74cdc13f036473
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=175d946ea00000
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+6d237e74cdc13f036473@xxxxxxxxxxxxxxxxxxxxxxxxx
> 
> usb 3-1: Direct firmware load for isl3887usb failed with error -2
> usb 3-1: Firmware not found.
> ==================================================================
> BUG: KASAN: slab-out-of-bounds in p54u_load_firmware_cb.cold+0x97/0x13d  
> drivers/net/wireless/intersil/p54/p54usb.c:936
> Read of size 8 at addr ffff8881c9cf7588 by task kworker/1:5/2759
> 
> CPU: 1 PID: 2759 Comm: kworker/1:5 Not tainted 5.2.0-rc5+ #11
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
> Google 01/01/2011
> Workqueue: events request_firmware_work_func
> Call Trace:
>   __dump_stack lib/dump_stack.c:77 [inline]
>   dump_stack+0xca/0x13e lib/dump_stack.c:113
>   print_address_description+0x67/0x231 mm/kasan/report.c:188
>   __kasan_report.cold+0x1a/0x32 mm/kasan/report.c:317
>   kasan_report+0xe/0x20 mm/kasan/common.c:614
>   p54u_load_firmware_cb.cold+0x97/0x13d  
> drivers/net/wireless/intersil/p54/p54usb.c:936
>   request_firmware_work_func+0x126/0x242  
> drivers/base/firmware_loader/main.c:785
>   process_one_work+0x905/0x1570 kernel/workqueue.c:2269
>   worker_thread+0x96/0xe20 kernel/workqueue.c:2415
>   kthread+0x30b/0x410 kernel/kthread.c:255
>   ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
> 
> Allocated by task 1612:
>   save_stack+0x1b/0x80 mm/kasan/common.c:71
>   set_track mm/kasan/common.c:79 [inline]
>   __kasan_kmalloc mm/kasan/common.c:489 [inline]
>   __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:462
>   kmalloc include/linux/slab.h:547 [inline]
>   syslog_print kernel/printk/printk.c:1346 [inline]
>   do_syslog kernel/printk/printk.c:1519 [inline]
>   do_syslog+0x4f4/0x12e0 kernel/printk/printk.c:1493
>   kmsg_read+0x8a/0xb0 fs/proc/kmsg.c:40
>   proc_reg_read+0x1c1/0x280 fs/proc/inode.c:221
>   __vfs_read+0x76/0x100 fs/read_write.c:425
>   vfs_read+0x18e/0x3d0 fs/read_write.c:461
>   ksys_read+0x127/0x250 fs/read_write.c:587
>   do_syscall_64+0xb7/0x560 arch/x86/entry/common.c:301
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
> 
> Freed by task 1612:
>   save_stack+0x1b/0x80 mm/kasan/common.c:71
>   set_track mm/kasan/common.c:79 [inline]
>   __kasan_slab_free+0x130/0x180 mm/kasan/common.c:451
>   slab_free_hook mm/slub.c:1421 [inline]
>   slab_free_freelist_hook mm/slub.c:1448 [inline]
>   slab_free mm/slub.c:2994 [inline]
>   kfree+0xd7/0x280 mm/slub.c:3949
>   syslog_print kernel/printk/printk.c:1405 [inline]
>   do_syslog kernel/printk/printk.c:1519 [inline]
>   do_syslog+0xff3/0x12e0 kernel/printk/printk.c:1493
>   kmsg_read+0x8a/0xb0 fs/proc/kmsg.c:40
>   proc_reg_read+0x1c1/0x280 fs/proc/inode.c:221
>   __vfs_read+0x76/0x100 fs/read_write.c:425
>   vfs_read+0x18e/0x3d0 fs/read_write.c:461
>   ksys_read+0x127/0x250 fs/read_write.c:587
>   do_syscall_64+0xb7/0x560 arch/x86/entry/common.c:301
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
> 
> The buggy address belongs to the object at ffff8881c9cf7180
>   which belongs to the cache kmalloc-1k of size 1024
> The buggy address is located 8 bytes to the right of
>   1024-byte region [ffff8881c9cf7180, ffff8881c9cf7580)
> The buggy address belongs to the page:
> page:ffffea0007273d00 refcount:1 mapcount:0 mapping:ffff8881dac02a00  
> index:0x0 compound_mapcount: 0
> flags: 0x200000000010200(slab|head)
> raw: 0200000000010200 dead000000000100 dead000000000200 ffff8881dac02a00
> raw: 0000000000000000 00000000000e000e 00000001ffffffff 0000000000000000
> page dumped because: kasan: bad access detected
> 
> Memory state around the buggy address:
>   ffff8881c9cf7480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>   ffff8881c9cf7500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > ffff8881c9cf7580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>                        ^
>   ffff8881c9cf7600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>   ffff8881c9cf7680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================

Isn't this the same as syzkaller bug 200d4bb11b23d929335f ?  Doesn't
the same patch fix it?

Alan Stern