On Wed, Apr 24, 2019 at 7:16 PM Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > [ Upstream commit 32a5ad9c22852e6bd9e74bdec5934ef9d1480bc5 ] > > Currently, when writing > > echo 18446744073709551616 > /proc/sys/fs/file-max > > /proc/sys/fs/file-max will overflow and be set to 0. That quickly > crashes the system. > > This commit sets the max and min value for file-max. The max value is > set to long int. Any higher value cannot currently be used as the > percpu counters are long ints and not unsigned integers. > > Note that the file-max value is ultimately parsed via > __do_proc_doulongvec_minmax(). This function does not report error when > min or max are exceeded. Which means if a value largen that long int is > written userspace will not receive an error instead the old value will be > kept. There is an argument to be made that this should be changed and > __do_proc_doulongvec_minmax() should return an error when a dedicated min > or max value are exceeded. However this has the potential to break > userspace so let's defer this to an RFC patch. > > Link: http://lkml.kernel.org/r/20190107222700.15954-3-christian@xxxxxxxxxx > Signed-off-by: Christian Brauner <christian@xxxxxxxxxx> > Acked-by: Kees Cook <keescook@xxxxxxxxxxxx> > Cc: Alexey Dobriyan <adobriyan@xxxxxxxxx> > Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> > Cc: Dominik Brodowski <linux@xxxxxxxxxxxxxxxxxxxx> > Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx> > Cc: Joe Lawrence <joe.lawrence@xxxxxxxxxx> > Cc: Luis Chamberlain <mcgrof@xxxxxxxxxx> > Cc: Waiman Long <longman@xxxxxxxxxx> > [christian@xxxxxxxxxx: v4] > Link: http://lkml.kernel.org/r/20190210203943.8227-3-christian@xxxxxxxxxx > Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> > Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> Hey Greg, Just an heads-up. This patch triggered a KASAN warning and Will has sent a fix for that which is already in master. So if you backport this patch you likely also want to backport 9002b21465fa4d829edfc94a5a441005cffaa972 (See https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=9002b21465fa4d829edfc94a5a441005cffaa972 ) Seems we missed a Cc: for stable in there. Sorry about that. Thanks! Christian > --- > kernel/sysctl.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/kernel/sysctl.c b/kernel/sysctl.c > index beadcf83ceba..2f98b11477b8 100644 > --- a/kernel/sysctl.c > +++ b/kernel/sysctl.c > @@ -126,6 +126,7 @@ static int __maybe_unused one = 1; > static int __maybe_unused two = 2; > static int __maybe_unused four = 4; > static unsigned long one_ul = 1; > +static unsigned long long_max = LONG_MAX; > static int one_hundred = 100; > #ifdef CONFIG_PRINTK > static int ten_thousand = 10000; > @@ -1603,6 +1604,8 @@ static struct ctl_table fs_table[] = { > .maxlen = sizeof(files_stat.max_files), > .mode = 0644, > .proc_handler = proc_doulongvec_minmax, > + .extra1 = &zero, > + .extra2 = &long_max, > }, > { > .procname = "nr_open", > -- > 2.19.1 > > >
