On Wed, Oct 16, 2019 at 06:42:10PM -0700, syzbot wrote: > Hello, > > syzbot found the following crash on: > > HEAD commit: 22be26f7 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=14f6dc5f600000 > kernel config: https://syzkaller.appspot.com/x/.config?x=387eccb7ac68ec5 > dashboard link: https://syzkaller.appspot.com/bug?extid=6fe95b826644f7f12b0b > compiler: gcc (GCC) 9.0.0 20181231 (experimental) > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=102c3227600000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12a503a0e00000 > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > Reported-by: syzbot+6fe95b826644f7f12b0b@xxxxxxxxxxxxxxxxxxxxxxxxx > > ldusb 1-1:0.28: Read buffer overflow, -131383859965943 bytes dropped This warning should be using %zu and thus read 18446612689849585673. Apparently, *actual_buffer holds a kernel address ffff8881cfb42000 instead of a transfer length. Possibly a stale value since the buffer is not cleared on allocation. > ================================================================== > BUG: KASAN: slab-out-of-bounds in _copy_to_user+0x124/0x150 > lib/usercopy.c:28 > Read of size 102391 at addr ffff8881cfb40008 by task syz-executor372/1737 And due to missing sanity checks the driver proceeds to access data beyond the ring-buffer entry. > CPU: 0 PID: 1737 Comm: syz-executor372 Not tainted 5.4.0-rc3+ #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS > Google 01/01/2011 > Call Trace: > __dump_stack lib/dump_stack.c:77 [inline] > dump_stack+0xca/0x13e lib/dump_stack.c:113 > print_address_description.constprop.0+0x36/0x50 mm/kasan/report.c:374 > __kasan_report.cold+0x1a/0x33 mm/kasan/report.c:506 > kasan_report+0xe/0x20 mm/kasan/common.c:634 > check_memory_region_inline mm/kasan/generic.c:185 [inline] > check_memory_region+0x128/0x190 mm/kasan/generic.c:192 > _copy_to_user+0x124/0x150 lib/usercopy.c:28 > copy_to_user include/linux/uaccess.h:152 [inline] > ld_usb_read+0x329/0x760 drivers/usb/misc/ldusb.c:492 > __vfs_read+0x76/0x100 fs/read_write.c:425 > vfs_read+0x1ea/0x430 fs/read_write.c:461 > ksys_read+0x1e8/0x250 fs/read_write.c:587 > do_syscall_64+0xb7/0x580 arch/x86/entry/common.c:290 > entry_SYSCALL_64_after_hwframe+0x49/0xbe > RIP: 0033:0x4421d9 > Code: e8 7c e7 ff ff 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 bb 07 fc ff c3 66 2e 0f 1f 84 00 00 00 00 > RSP: 002b:00007ffc08eb0888 EFLAGS: 00000246 ORIG_RAX: 0000000000000000 > RAX: ffffffffffffffda RBX: 00007ffc08eb0ae0 RCX: 00000000004421d9 > RDX: 0000000000018ff7 RSI: 0000000020000a80 RDI: 0000000000000004 > RBP: 0000000000000000 R08: 000000000000000f R09: 0000000000402eb0 > R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 > R13: 0000000000402eb0 R14: 0000000000000000 R15: 0000000000000000 > > The buggy address belongs to the page: > page:ffffea00073ed000 refcount:1 mapcount:0 mapping:0000000000000000 > index:0x0 compound_mapcount: 0 > flags: 0x200000000010000(head) > raw: 0200000000010000 dead000000000100 dead000000000122 0000000000000000 > raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000 > page dumped because: kasan: bad access detected > > Memory state around the buggy address: > ffff8881cfb55500: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > ffff8881cfb55580: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > > ffff8881cfb55600: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe > ^ > ffff8881cfb55680: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe > ffff8881cfb55700: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe > ================================================================== The drivers ring-buffer implementation is broken so this could potentially be a memory-ordering issue (e.g. the entry is read before it has been updated). Let's try the below. Johan #syz test: https://github.com/google/kasan.git 22be26f7 >From 61c87ec9b1311949e313f633e84aab5c73975078 Mon Sep 17 00:00:00 2001 From: Johan Hovold <johan@xxxxxxxxxx> Date: Thu, 17 Oct 2019 11:53:04 +0200 Subject: [PATCH] wip: USB: lsusb: fix ring-buffer locking Signed-off-by: Johan Hovold <johan@xxxxxxxxxx> --- drivers/usb/misc/ldusb.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) diff --git a/drivers/usb/misc/ldusb.c b/drivers/usb/misc/ldusb.c index f3108d85e768..c8d09ac7ade9 100644 --- a/drivers/usb/misc/ldusb.c +++ b/drivers/usb/misc/ldusb.c @@ -467,7 +467,7 @@ static ssize_t ld_usb_read(struct file *file, char __user *buffer, size_t count, /* wait for data */ spin_lock_irq(&dev->rbsl); - if (dev->ring_head == dev->ring_tail) { + while (dev->ring_head == dev->ring_tail) { dev->interrupt_in_done = 0; spin_unlock_irq(&dev->rbsl); if (file->f_flags & O_NONBLOCK) { @@ -477,8 +477,8 @@ static ssize_t ld_usb_read(struct file *file, char __user *buffer, size_t count, retval = wait_event_interruptible(dev->read_wait, dev->interrupt_in_done); if (retval < 0) goto unlock_exit; - } else { - spin_unlock_irq(&dev->rbsl); + + spin_lock_irq(&dev->rbsl); } /* actual_buffer contains actual_length + interrupt_in_buffer */ @@ -487,17 +487,19 @@ static ssize_t ld_usb_read(struct file *file, char __user *buffer, size_t count, if (bytes_to_read < *actual_buffer) dev_warn(&dev->intf->dev, "Read buffer overflow, %zd bytes dropped\n", *actual_buffer-bytes_to_read); + spin_unlock_irq(&dev->rbsl); /* copy one interrupt_in_buffer from ring_buffer into userspace */ if (copy_to_user(buffer, actual_buffer+1, bytes_to_read)) { retval = -EFAULT; goto unlock_exit; } - dev->ring_tail = (dev->ring_tail+1) % ring_buffer_size; - retval = bytes_to_read; spin_lock_irq(&dev->rbsl); + + dev->ring_tail = (dev->ring_tail+1) % ring_buffer_size; + if (dev->buffer_overflow) { dev->buffer_overflow = 0; spin_unlock_irq(&dev->rbsl); @@ -693,12 +695,17 @@ static int ld_usb_probe(struct usb_interface *intf, const struct usb_device_id * dev_warn(&intf->dev, "Interrupt out endpoint not found (using control endpoint instead)\n"); dev->interrupt_in_endpoint_size = usb_endpoint_maxp(dev->interrupt_in_endpoint); + dev_info(&intf->dev, "%s - interrupt_in_endpoint_size = %zu\n", + __func__, dev->interrupt_in_endpoint_size); dev->ring_buffer = kmalloc_array(ring_buffer_size, sizeof(size_t) + dev->interrupt_in_endpoint_size, GFP_KERNEL); if (!dev->ring_buffer) goto error; + dev_info(&intf->dev, "%s - ring_buffer = %px\n", __func__, + dev->ring_buffer); + dev->interrupt_in_buffer = kmalloc(dev->interrupt_in_endpoint_size, GFP_KERNEL); if (!dev->interrupt_in_buffer) goto error; -- 2.23.0
