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Date: Fri, 2 Dec 2016 14:54:32 +0800 From: Yisheng Xie <xieyisheng1@...wei.com> To: Andrew Morton <akpm@...ux-foundation.org> CC: <linux-kernel@...r.kernel.org>, <acme@...hat.com>, <mgorman@...hsingularity.net>, <viro@...iv.linux.org.uk>, <hannes@...xchg.org>, <ebiederm@...ssion.com>, <bristot@...hat.com>, <subashab@...eaurora.org>, <dcashman@...gle.com>, <w@....eu>, <arnd@...db.de>, <guohanjun@...wei.com>, <qiuxishi@...wei.com> Subject: Re: [PATCH] kernel/sysctl: return -EINVAL if write invalid val to ulong type sysctl On 2016/12/1 5:33, Andrew Morton wrote: > On Wed, 30 Nov 2016 18:30:52 +0800 Yisheng Xie <xieyisheng1@...wei.com> wrote: > >> I tried to echo an invalid value to an unsigned long type sysctl on >> 4.9.0-rc6: >> linux:~# cat /proc/sys/vm/user_reserve_kbytes >> 131072 >> linux:~# echo -1 > /proc/sys/vm/user_reserve_kbytes >> linux:~# cat /proc/sys/vm/user_reserve_kbytes >> 131072 >> >> The echo operation got error and the value do not write to >> user_reserve_kbytes, however, user do not know it until checking >> the value again. >> >> This patch return -EINVAL when write an invalid value to unsigned >> long type sysctl to make user know what happened without >> checking its value once more, just as what proc_douintvec do. > > hmpf. > > # echo 18446744073709551615 > /proc/sys/vm/user_reserve_kbytes > # cat /proc/sys/vm/user_reserve_kbytes > 18446744073709551615 > > I think that when taking in an unsigned long the kernel should simply > treat -1 as 0xffffffff (or 0xffffffffffffffff). It's natural and > normal and everyone knows what it means? > Hi Andrew, Thank you for your reply. Do you means it should be like this: # echo -1 > /proc/sys/vm/user_reserve_kbytes # cat /proc/sys/vm/user_reserve_kbytes 18446744073709551615 I looks ok to me, however, I not sure whether other code in the kernel will also use its complement if user write a negative number for an unsigned long. Does anyone have other opinion ? Thanks Yisheng Xie. > > > > . >
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