Re: [PATCH] cfg80211: fix for duplicate response for driver reg request

[Johannes Berg <johannes@sipsolutions.net>]

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On Mon, 2009-06-08 at 18:54 -0700, Luis R. Rodriguez wrote:
> As Pavel puts userspace can be stupid and should not
> cause kernel crashes. In this case Pavel was able to
> find a crash here but unable to reproduce. Either way
> lets deal with this.

Yes. Userspace is allowed to be as stupid as it wants, and may _never_
cause a kernel bug.

johannes

> This should fix:
> 
> ------------[ cut here ]------------
> kernel BUG at /home/proski/src/linux-2.6/net/wireless/reg.c:2132!
> Oops: Exception in kernel mode, sig: 5 [#1]
> PowerMac
> Modules linked in: ath5k ath [last unloaded: scsi_wait_scan]
> NIP: c02f3eac LR: c02f3d08 CTR: 00000000
> REGS: ef107aa0 TRAP: 0700   Not tainted  (2.6.30-rc8-wl)
> MSR: 00029032 <EE,ME,CE,IR,DR>  CR: 88002442  XER: 20000000
> TASK = ef84acb0[834] 'crda' THREAD: ef106000
> GPR00: ef953840 ef107b50 ef84acb0 ef1380bc 00000006 c035a5c8 ef107b90 c035a5c8
> GPR08: 00080005 efb68980 c0445628 ef130004 28002422 10019ce0 10012d3c 00000001
> GPR16: 1070b2ac 00000005 48023558 1070b380 4802304c 00000000 ef107ddc c035a5c8
> GPR24: ef107b78 c0443350 ef8bcb00 00000005 ef138080 c04a6a70 c04a0000 ef8bcb00
> NIP [c02f3eac] set_regdom+0x4c4/0x4ec
> LR [c02f3d08] set_regdom+0x320/0x4ec
> Call Trace:
> [ef107b50] [c02f3d08] set_regdom+0x320/0x4ec (unreliable)
> [ef107b70] [c02f9d10] nl80211_set_reg+0x140/0x2d0
> [ef107bc0] [c02aa2b8] genl_rcv_msg+0x204/0x228
> [ef107c10] [c02a97cc] netlink_rcv_skb+0xe8/0x10c
> [ef107c30] [c02aa094] genl_rcv+0x3c/0x5c
> [ef107c40] [c02a9050] netlink_unicast+0x308/0x36c
> [ef107c80] [c02a92bc] netlink_sendmsg+0x208/0x2f0
> [ef107cd0] [c0282048] sock_sendmsg+0xac/0xe4
> [ef107db0] [c02822b4] sys_sendmsg+0x234/0x2d8
> [ef107f00] [c0283a88] sys_socketcall+0x108/0x258
> [ef107f40] [c0012790] ret_from_syscall+0x0/0x38
> --- Exception: c01 at 0xfa6b3b4
>    LR = 0xfb4b5d4
> Instruction dump:
> 80690000 4bffc1e9 2c030000 4182003c 88a30039 88830038 3c60c03c 38632a18
> 4802c20d 4bfffed0 7f83e378 8403003c <0f000000> 7fe4fb78 4bffe6d1 7c7b1b79
> ---[ end trace c8eebdfbe3eb31de ]---
> 
> Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
> ---
>  net/wireless/reg.c |    7 ++++++-
>  1 files changed, 6 insertions(+), 1 deletions(-)
> 
> diff --git a/net/wireless/reg.c b/net/wireless/reg.c
> index ea4c299..5e14371 100644
> --- a/net/wireless/reg.c
> +++ b/net/wireless/reg.c
> @@ -2129,7 +2129,12 @@ static int __set_regdom(const struct ieee80211_regdomain *rd)
>  		 * driver wanted to the wiphy to deal with conflicts
>  		 */
>  
> -		BUG_ON(request_wiphy->regd);
> +		/*
> +		 * Userspace could have sent two replies with only
> +		 * one kernel request.
> +		 */
> +		if (request_wiphy->regd)
> +			return -EALREADY;
>  
>  		r = reg_copy_regd(&request_wiphy->regd, rd);
>  		if (r)

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