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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:
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|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| firmware | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
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.