This is a note to let you know that I've just added the patch titled
USB: gadget: fix illegal array access in binding with UDC
to my usb git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git in the usb-linus branch.
The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)
The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.
If you have any questions about this process, please let me know.
From 15753588bcd4bbffae1cca33c8ced5722477fe1f Mon Sep 17 00:00:00 2001
From: Kyungtae Kim kt0755@gmail.com Date: Sun, 10 May 2020 05:43:34 +0000 Subject: USB: gadget: fix illegal array access in binding with UDC
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@gmail.com Reported-and-tested-by: Kyungtae Kim kt0755@gmail.com Cc: Felipe Balbi balbi@kernel.org Cc: stable stable@vger.kernel.org Link: https://lore.kernel.org/r/20200510054326.GA19198@pizza01 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- 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, char *name; int ret;
+ if (strlen(page) < len) + return -EOVERFLOW; + name = kstrdup(page, GFP_KERNEL); if (!name) return -ENOMEM;