From 1a087f032111a88e826877449dfb93ceb22b78b9 Mon Sep 17 00:00:00 2001 From: Xinyong Date: Fri, 2 Mar 2018 19:20:07 +0800 Subject: usb: gadget: f_fs: Fix use-after-free in ffs_fs_kill_sb() When I debug a kernel crash issue in funcitonfs, found ffs_data.ref overflowed, While functionfs is unmounting, ffs_data is put twice. Commit 43938613c6fd ("drivers, usb: convert ffs_data.ref from atomic_t to refcount_t") can avoid refcount overflow, but that is risk some situations. So no need put ffs data in ffs_fs_kill_sb, already put in ffs_data_closed. The issue can be reproduced in Mediatek mt6763 SoC, ffs for ADB device. KASAN enabled configuration reports use-after-free errro. BUG: KASAN: use-after-free in refcount_dec_and_test+0x14/0xe0 at addr ffffffc0579386a0 Read of size 4 by task umount/4650 ==================================================== BUG kmalloc-512 (Tainted: P W O ): kasan: bad access detected ----------------------------------------------------------------------------- INFO: Allocated in ffs_fs_mount+0x194/0x844 age=22856 cpu=2 pid=566 alloc_debug_processing+0x1ac/0x1e8 ___slab_alloc.constprop.63+0x640/0x648 __slab_alloc.isra.57.constprop.62+0x24/0x34 kmem_cache_alloc_trace+0x1a8/0x2bc ffs_fs_mount+0x194/0x844 mount_fs+0x6c/0x1d0 vfs_kern_mount+0x50/0x1b4 do_mount+0x258/0x1034 INFO: Freed in ffs_data_put+0x25c/0x320 age=0 cpu=3 pid=4650 free_debug_processing+0x22c/0x434 __slab_free+0x2d8/0x3a0 kfree+0x254/0x264 ffs_data_put+0x25c/0x320 ffs_data_closed+0x124/0x15c ffs_fs_kill_sb+0xb8/0x110 deactivate_locked_super+0x6c/0x98 deactivate_super+0xb0/0xbc INFO: Object 0xffffffc057938600 @offset=1536 fp=0x (null) ...... Call trace: [] dump_backtrace+0x0/0x250 [] show_stack+0x14/0x1c [] dump_stack+0xa0/0xc8 [] print_trailer+0x158/0x260 [] object_err+0x3c/0x40 [] kasan_report_error+0x2a8/0x754 [] kasan_report+0x5c/0x60 [] __asan_load4+0x70/0x88 [] refcount_dec_and_test+0x14/0xe0 [] ffs_data_put+0x80/0x320 [] ffs_fs_kill_sb+0xc8/0x110 [] deactivate_locked_super+0x6c/0x98 [] deactivate_super+0xb0/0xbc [] cleanup_mnt+0x64/0xec [] __cleanup_mnt+0x10/0x18 [] task_work_run+0xcc/0x124 [] do_notify_resume+0x60/0x70 [] work_pending+0x10/0x14 Cc: stable@vger.kernel.org Signed-off-by: Xinyong Signed-off-by: Felipe Balbi --- drivers/usb/gadget/function/f_fs.c | 1 - 1 file changed, 1 deletion(-) (limited to 'drivers/usb') diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c index c2592d883f67..d2428a9e8900 100644 --- a/drivers/usb/gadget/function/f_fs.c +++ b/drivers/usb/gadget/function/f_fs.c @@ -1538,7 +1538,6 @@ ffs_fs_kill_sb(struct super_block *sb) if (sb->s_fs_info) { ffs_release_dev(sb->s_fs_info); ffs_data_closed(sb->s_fs_info); - ffs_data_put(sb->s_fs_info); } } -- cgit v1.2.3-59-g8ed1b