Sriharsha Allenki
e550fa72dd
commit3c6f8cb92cupstream. On platforms with IOMMU enabled, multiple SGs can be coalesced into one by the IOMMU driver. In that case the SG list processing as part of the completion of a urb on a bulk endpoint can result into a NULL pointer dereference with the below stack dump. <6> Unable to handle kernel NULL pointer dereference at virtual address 0000000c <6> pgd = c0004000 <6> [0000000c] *pgd=00000000 <6> Internal error: Oops: 5 [#1] PREEMPT SMP ARM <2> PC is at xhci_queue_bulk_tx+0x454/0x80c <2> LR is at xhci_queue_bulk_tx+0x44c/0x80c <2> pc : [<c08907c4>] lr : [<c08907bc>] psr: 000000d3 <2> sp : ca337c80 ip : 00000000 fp : ffffffff <2> r10: 00000000 r9 : 50037000 r8 : 00004000 <2> r7 : 00000000 r6 : 00004000 r5 : 00000000 r4 : 00000000 <2> r3 : 00000000 r2 : 00000082 r1 : c2c1a200 r0 : 00000000 <2> Flags: nzcv IRQs off FIQs off Mode SVC_32 ISA ARM Segment none <2> Control: 10c0383d Table: b412c06a DAC: 00000051 <6> Process usb-storage (pid: 5961, stack limit = 0xca336210) <snip> <2> [<c08907c4>] (xhci_queue_bulk_tx) <2> [<c0881b3c>] (xhci_urb_enqueue) <2> [<c0831068>] (usb_hcd_submit_urb) <2> [<c08350b4>] (usb_sg_wait) <2> [<c089f384>] (usb_stor_bulk_transfer_sglist) <2> [<c089f2c0>] (usb_stor_bulk_srb) <2> [<c089fe38>] (usb_stor_Bulk_transport) <2> [<c089f468>] (usb_stor_invoke_transport) <2> [<c08a11b4>] (usb_stor_control_thread) <2> [<c014a534>] (kthread) The above NULL pointer dereference is the result of block_len and the sent_len set to zero after the first SG of the list when IOMMU driver is enabled. Because of this the loop of processing the SGs has run more than num_sgs which resulted in a sg_next on the last SG of the list which has SG_END set. Fix this by check for the sg before any attributes of the sg are accessed. [modified reason for null pointer dereference in commit message subject -Mathias] Fixes:f9c589e142("xhci: TD-fragment, align the unsplittable case with a bounce buffer") Cc: stable@vger.kernel.org Signed-off-by: Sriharsha Allenki <sallenki@codeaurora.org> Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com> Link: https://lore.kernel.org/r/20200514110432.25564-2-mathias.nyman@linux.intel.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To understand all the Linux-USB framework, you'll use these resources:
* This source code. This is necessarily an evolving work, and
includes kerneldoc that should help you get a current overview.
("make pdfdocs", and then look at "usb.pdf" for host side and
"gadget.pdf" for peripheral side.) Also, Documentation/usb has
more information.
* The USB 2.0 specification (from www.usb.org), with supplements
such as those for USB OTG and the various device classes.
The USB specification has a good overview chapter, and USB
peripherals conform to the widely known "Chapter 9".
* Chip specifications for USB controllers. Examples include
host controllers (on PCs, servers, and more); peripheral
controllers (in devices with Linux firmware, like printers or
cell phones); and hard-wired peripherals like Ethernet adapters.
* Specifications for other protocols implemented by USB peripheral
functions. Some are vendor-specific; others are vendor-neutral
but just standardized outside of the www.usb.org team.
Here is a list of what each subdirectory here is, and what is contained in
them.
core/ - This is for the core USB host code, including the
usbfs files and the hub class driver ("hub_wq").
host/ - This is for USB host controller drivers. This
includes UHCI, OHCI, EHCI, and others that might
be used with more specialized "embedded" systems.
gadget/ - This is for USB peripheral controller drivers and
the various gadget drivers which talk to them.
Individual USB driver directories. A new driver should be added to the
first subdirectory in the list below that it fits into.
image/ - This is for still image drivers, like scanners or
digital cameras.
../input/ - This is for any driver that uses the input subsystem,
like keyboard, mice, touchscreens, tablets, etc.
../media/ - This is for multimedia drivers, like video cameras,
radios, and any other drivers that talk to the v4l
subsystem.
../net/ - This is for network drivers.
serial/ - This is for USB to serial drivers.
storage/ - This is for USB mass-storage drivers.
class/ - This is for all USB device drivers that do not fit
into any of the above categories, and work for a range
of USB Class specified devices.
misc/ - This is for all USB device drivers that do not fit
into any of the above categories.