lkml.org 
[lkml]   [2006]   [Aug]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] getsockopt() early argument sanity checking
Arjan wrote:

>> We're on UP. sys_getsockopt() does get_user() (due to the patch) and
>> makes sure that the passed *optlen is sane. Even if this get_user()
>> sleeps, the value it returns in "len" is what's currently in memory at
>> the time of the get_user() return (correct?) Then an underlying
>> *getsockopt() function does another get_user() on optlen (same address),
>> without doing any other user-space data accesses or anything else that
>> could sleep first. Is it possible that this second get_user()
>> invocation would sleep? I think not since it's the same address that
>> we've just read a value from, we did not leave kernel space, and we're
>> on UP (so no other processor could have changed the mapping). So the
>> patch appears to be sufficient for this special case (which is not
>> unlikely).
>
>this reasoning goes out the window with kernel preemption of course ;)
>
>
Or O_DIRECT? I'm not sure what's easier to time, a kernel preemption or
a DMA to the user address.

--
Manfred

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2006-08-20 21:01    [W:0.105 / U:0.184 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site