On 31.07.2013 18:37, Eric Dumazet wrote:
On Wed, 2013-07-31 at 17:57 +0400, Roman Gushchin wrote:
It's possible to assign an invalid value to the net.core.somaxconn
sysctl variable, because there is no checks at all.
The sk_max_ack_backlog field of the sock structure is defined as
unsigned short. Therefore, the backlog argument in inet_listen()
shouldn't exceed USHRT_MAX. The backlog argument in the listen() syscall
is truncated to the somaxconn value. So, the somaxconn value shouldn't
exceed 65535 (USHRT_MAX).
Also, negative values of somaxconn are meaningless.
before:
$ sysctl -w net.core.somaxconn=256
net.core.somaxconn = 256
$ sysctl -w net.core.somaxconn=65536
net.core.somaxconn = 65536
$ sysctl -w net.core.somaxconn=-100
net.core.somaxconn = -100
after:
$ sysctl -w net.core.somaxconn=256
net.core.somaxconn = 256
$ sysctl -w net.core.somaxconn=65536
error: "Invalid argument" setting key "net.core.somaxconn"
$ sysctl -w net.core.somaxconn=-100
error: "Invalid argument" setting key "net.core.somaxconn"
Signed-off-by: Roman Gushchin <[email protected]>
---
net/core/sysctl_net_core.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
We had a discussion about this one month ago, as Changli Gao posted a
patch. http://patchwork.ozlabs.org/patch/255460/
So proper credits would be nice ;)
Ok :)
Based on a prior patch from Changli Gao
Reported-by: Changli Gao <[email protected]>
Suggested-by: Eric Dumazet <[email protected]>
Acked-by: Eric Dumazet <[email protected]>
Thanks!
PS I've forwarded your letter back to the lkml by mistake.
Sorry)
Regards,
Roman
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