Kyungtae Kim <kt0755@xxxxxxxxx> writes: > FuzzUSB (a variant of syzkaller) found an illegal array access > using an incorrect index while binding a gadget with UDC. > > Reference: https://www.spinics.net/lists/linux-usb/msg194331.html > > This bug occurs when a size variable used for a buffer > is misused to access its strcpy-ed buffer. > Given a buffer along with its size variable (taken from user input), > from which, a new buffer is created using kstrdup(). > Due to the original buffer containing 0 value in the middle, > the size of the kstrdup-ed buffer becomes smaller than that of the original. > So accessing the kstrdup-ed buffer with the same size variable > triggers memory access violation. > > The fix makes sure no zero value in the buffer, > by comparing the strlen() of the orignal buffer with the size variable, > so that the access to the kstrdup-ed buffer is safe. > > > BUG: KASAN: slab-out-of-bounds in gadget_dev_desc_UDC_store+0x1ba/0x200 > drivers/usb/gadget/configfs.c:266 > Read of size 1 at addr ffff88806a55dd7e by task syz-executor.0/17208 > > CPU: 2 PID: 17208 Comm: syz-executor.0 Not tainted 5.6.8 #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+0xce/0x128 lib/dump_stack.c:118 > print_address_description.constprop.4+0x21/0x3c0 mm/kasan/report.c:374 > __kasan_report+0x131/0x1b0 mm/kasan/report.c:506 > kasan_report+0x12/0x20 mm/kasan/common.c:641 > __asan_report_load1_noabort+0x14/0x20 mm/kasan/generic_report.c:132 > gadget_dev_desc_UDC_store+0x1ba/0x200 drivers/usb/gadget/configfs.c:266 > flush_write_buffer fs/configfs/file.c:251 [inline] > configfs_write_file+0x2f1/0x4c0 fs/configfs/file.c:283 > __vfs_write+0x85/0x110 fs/read_write.c:494 > vfs_write+0x1cd/0x510 fs/read_write.c:558 > ksys_write+0x18a/0x220 fs/read_write.c:611 > __do_sys_write fs/read_write.c:623 [inline] > __se_sys_write fs/read_write.c:620 [inline] > __x64_sys_write+0x73/0xb0 fs/read_write.c:620 > do_syscall_64+0x9e/0x510 arch/x86/entry/common.c:294 > entry_SYSCALL_64_after_hwframe+0x49/0xbe > > > Signed-off-by: Kyungtae Kim <kt0755@xxxxxxxxx> > Reported-and-tested-by: Kyungtae Kim <kt0755@xxxxxxxxx> > > --- > drivers/usb/gadget/configfs.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/usb/gadget/configfs.c b/drivers/usb/gadget/configfs.c > index 32b637e3e1fa..6a9aa4413d64 100644 > --- a/drivers/usb/gadget/configfs.c > +++ b/drivers/usb/gadget/configfs.c > @@ -260,6 +260,9 @@ static ssize_t gadget_dev_desc_UDC_store(struct > config_item *item, patch is line-wrapped, please fix and resend. -- balbi
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