On Thu, 2015-08-13 at 11:21 +0100, Andy Whitcroft wrote:
> When generating /proc/net/route we emit a header followed by a line for
> each route. When a short read is performed we will restart this process
> based on the open file descriptor. When calculating the start point we
> fail to take into account that the 0th entry is the header. This leads
> us to skip the first entry when doing a continuation read.
>
> This can be easily seen with the comparison below:
>
> while read l; do echo "$l"; done </proc/net/route >A
> cat /proc/net/route >B
> diff -bu A B | grep '^[+-]'
>
> On my example machine I have approximatly 10KB of route output. There we
> see the very first non-title element is lost in the while read case,
> and an entry around the 8K mark in the cat case:
>
> +wlan0 00000000 02021EAC 0003 0 0 400 00000000 0 0 0
> -tun1 00C0AC0A 00000000 0001 0 0 950 00C0FFFF 0 0 0
>
> Fix up the off-by-one when reaquiring position on continuation.
>
> BugLink: http://bugs.launchpad.net/bugs/1483440
> Signed-off-by: Andy Whitcroft <[email protected]>
> ---
> net/ipv4/fib_trie.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> From code inspection I belive this was introduced by the Fixes
> below, but I have not tested this to confirm.
>
> Fixes: 8be33e955cb9 ("ipv4: off-by-one in continuation handling in
> /proc/net/route")
You probably meant
Fixes: 8be33e955cb9 ("fib_trie: Fib walk rcu should take a tnode and key
instead of a trie and a leaf")
CC Alexander for review/comment
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