From b946777664dba9e3d5712073c173544c12762351 Mon Sep 17 00:00:00 2001 From: Alan Stern Date: Fri, 9 Dec 2016 15:17:46 -0500 Subject: [PATCH] USB: gadgetfs: fix unbounded memory allocation bug commit faab50984fe6636e616c7cc3d30308ba391d36fd upstream. Andrey Konovalov reports that fuzz testing with syzkaller causes a KASAN warning in gadgetfs: BUG: KASAN: slab-out-of-bounds in dev_config+0x86f/0x1190 at addr ffff88003c47e160 Write of size 65537 by task syz-executor0/6356 CPU: 3 PID: 6356 Comm: syz-executor0 Not tainted 4.9.0-rc7+ #19 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 ffff88003c107ad8 ffffffff81f96aba ffffffff3dc11ef0 1ffff10007820eee ffffed0007820ee6 ffff88003dc11f00 0000000041b58ab3 ffffffff8598b4c8 ffffffff81f96828 ffffffff813fb4a0 ffff88003b6eadc0 ffff88003c107738 Call Trace: [< inline >] __dump_stack lib/dump_stack.c:15 [] dump_stack+0x292/0x398 lib/dump_stack.c:51 [] kasan_object_err+0x1c/0x70 mm/kasan/report.c:159 [< inline >] print_address_description mm/kasan/report.c:197 [] kasan_report_error+0x1f0/0x4e0 mm/kasan/report.c:286 [] kasan_report+0x35/0x40 mm/kasan/report.c:306 [< inline >] check_memory_region_inline mm/kasan/kasan.c:308 [] check_memory_region+0x139/0x190 mm/kasan/kasan.c:315 [] kasan_check_write+0x14/0x20 mm/kasan/kasan.c:326 [< inline >] copy_from_user arch/x86/include/asm/uaccess.h:689 [< inline >] ep0_write drivers/usb/gadget/legacy/inode.c:1135 [] dev_config+0x86f/0x1190 drivers/usb/gadget/legacy/inode.c:1759 [] __vfs_write+0x5d5/0x760 fs/read_write.c:510 [] vfs_write+0x170/0x4e0 fs/read_write.c:560 [< inline >] SYSC_write fs/read_write.c:607 [] SyS_write+0xfb/0x230 fs/read_write.c:599 [] entry_SYSCALL_64_fastpath+0x1f/0xc2 Indeed, there is a comment saying that the value of len is restricted to a 16-bit integer, but the code doesn't actually do this. This patch fixes the warning. It replaces the comment with a computation that forces the amount of data copied from the user in ep0_write() to be no larger than the wLength size for the control transfer, which is a 16-bit quantity. Signed-off-by: Alan Stern Reported-by: Andrey Konovalov Tested-by: Andrey Konovalov Signed-off-by: Felipe Balbi Signed-off-by: Greg Kroah-Hartman --- drivers/usb/gadget/legacy/inode.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/usb/gadget/legacy/inode.c b/drivers/usb/gadget/legacy/inode.c index 298886b4036134..e597534d23ac39 100644 --- a/drivers/usb/gadget/legacy/inode.c +++ b/drivers/usb/gadget/legacy/inode.c @@ -1126,7 +1126,7 @@ ep0_write (struct file *fd, const char __user *buf, size_t len, loff_t *ptr) /* data and/or status stage for control request */ } else if (dev->state == STATE_DEV_SETUP) { - /* IN DATA+STATUS caller makes len <= wLength */ + len = min_t(size_t, len, dev->setup_wLength); if (dev->setup_in) { retval = setup_req (dev->gadget->ep0, dev->req, len); if (retval == 0) {