202a0a70e4
When the frame check sequence (FCS) is split across the last two frames of a fragmented packet, part of the FCS gets counted twice, once when subtracting the FCS, and again when subtracting the previously received data. For example, if 1602 bytes are received, and the first fragment contains the first 1600 bytes (including the first two bytes of the FCS), and the second fragment contains the last two bytes of the FCS: 'skb->len == 1600' from the first fragment size = lstatus & BD_LENGTH_MASK; # 1602 size -= ETH_FCS_LEN; # 1598 size -= skb->len; # -2 Since the size is unsigned, it wraps around and causes a BUG later in the packet handling, as shown below: kernel BUG at ./include/linux/skbuff.h:2068! Oops: Exception in kernel mode, sig: 5 [#1] ... NIP [c021ec60] skb_pull+0x24/0x44 LR [c01e2fbc] gfar_clean_rx_ring+0x498/0x690 Call Trace: [df7edeb0] [c01e2c1c] gfar_clean_rx_ring+0xf8/0x690 (unreliable) [df7edf20] [c01e33a8] gfar_poll_rx_sq+0x3c/0x9c [df7edf40] [c023352c] net_rx_action+0x21c/0x274 [df7edf90] [c0329000] __do_softirq+0xd8/0x240 [df7edff0] [c000c108] call_do_irq+0x24/0x3c [c0597e90] [c00041dc] do_IRQ+0x64/0xc4 [c0597eb0] [c000d920] ret_from_except+0x0/0x18 --- interrupt: 501 at arch_cpu_idle+0x24/0x5c Change the size to a signed integer and then trim off any part of the FCS that was received prior to the last fragment. Fixes: 6c389fc931bc ("gianfar: fix size of scatter-gathered frames") Signed-off-by: Andy Spencer <aspencer@spacex.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.