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FuzzUSB (a variant of syzkaller) found a free-while-still-in-use bug in the USB scatter-gather library: BUG: KASAN: use-after-free in atomic_read include/asm-generic/atomic-instrumented.h:26 [inline] BUG: KASAN: use-after-free in usb_hcd_unlink_urb+0x5f/0x170 drivers/usb/core/hcd.c:1607 Read of size 4 at addr ffff888065379610 by task kworker/u4:1/27 CPU: 1 PID: 27 Comm: kworker/u4:1 Not tainted 5.5.11 #2 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014 Workqueue: scsi_tmf_2 scmd_eh_abort_handler 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+0x153/0x1cb mm/kasan/report.c:506 kasan_report+0x12/0x20 mm/kasan/common.c:639 check_memory_region_inline mm/kasan/generic.c:185 [inline] check_memory_region+0x152/0x1b0 mm/kasan/generic.c:192 __kasan_check_read+0x11/0x20 mm/kasan/common.c:95 atomic_read include/asm-generic/atomic-instrumented.h:26 [inline] usb_hcd_unlink_urb+0x5f/0x170 drivers/usb/core/hcd.c:1607 usb_unlink_urb+0x72/0xb0 drivers/usb/core/urb.c:657 usb_sg_cancel+0x14e/0x290 drivers/usb/core/message.c:602 usb_stor_stop_transport+0x5e/0xa0 drivers/usb/storage/transport.c:937 This bug occurs when cancellation of the S-G transfer races with transfer completion. When that happens, usb_sg_cancel() may continue to access the transfer's URBs after usb_sg_wait() has freed them. The bug is caused by the fact that usb_sg_cancel() does not take any sort of reference to the transfer, and so there is nothing to prevent the URBs from being deallocated while the routine is trying to use them. The fix is to take such a reference by incrementing the transfer's io->count field while the cancellation is in progres and decrementing it afterward. The transfer's URBs are not deallocated until io->complete is triggered, which happens when io->count reaches zero. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Reported-and-tested-by: Kyungtae Kim <kt0755@gmail.com> CC: <stable@vger.kernel.org> Link: https://lore.kernel.org/r/Pine.LNX.4.44L0.2003281615140.14837-100000@netrider.rowland.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.