| Message ID | 1519706711-18580-2-git-send-email-me@tobin.cc (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Hi Tobin, On Tue, Feb 27, 2018 at 03:45:09PM +1100, Tobin C. Harding wrote: > When the system is idle it is likely that most files under /proc/PID > will be identical for various processes. Scanning _all_ the PIDs under > /proc is unnecessary and implies that we are thoroughly scanning /proc. > This is _not_ the case because there may be ways userspace can trigger > creation of /proc files that leak addresses but were not present during > a scan. For these two reasons we should exclude all PID directories > under /proc except '1/' > > Exclude all /proc/PID except /proc/1. > > Signed-off-by: Tobin C. Harding <me@tobin.cc> > --- > scripts/leaking_addresses.pl | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/scripts/leaking_addresses.pl b/scripts/leaking_addresses.pl > index 6e5bc57caeaa..fb40e2828f43 100755 > --- a/scripts/leaking_addresses.pl > +++ b/scripts/leaking_addresses.pl > @@ -10,6 +10,14 @@ > # Use --debug to output path before parsing, this is useful to find files that > # cause the script to choke. > > +# > +# When the system is idle it is likely that most files under /proc/PID will be > +# identical for various processes. Scanning _all_ the PIDs under /proc is > +# unnecessary and implies that we are thoroughly scanning /proc. This is _not_ > +# the case because there may be ways userspace can trigger creation of /proc > +# files that leak addresses but were not present during a scan. For these two > +# reasons we exclude all PID directories under /proc except '1/' > + > use warnings; > use strict; > use POSIX; > @@ -472,6 +480,9 @@ sub walk > my $path = "$pwd/$file"; > next if (-l $path); > > + # skip /proc/PID except /proc/1 > + next if ($path =~ /\/proc\/(?:[2-9][0-9]*|1[0-9]+)/); Can't we just do, substr($path, 0, len("/proc/1/")) eq "/proc/1/" ? seems much easier to read than the regex. Cheers, Tycho
On Mon, Feb 26, 2018 at 10:09:31PM -0700, Tycho Andersen wrote: > Hi Tobin, > > On Tue, Feb 27, 2018 at 03:45:09PM +1100, Tobin C. Harding wrote: > > When the system is idle it is likely that most files under /proc/PID > > will be identical for various processes. Scanning _all_ the PIDs under > > /proc is unnecessary and implies that we are thoroughly scanning /proc. > > This is _not_ the case because there may be ways userspace can trigger > > creation of /proc files that leak addresses but were not present during > > a scan. For these two reasons we should exclude all PID directories > > under /proc except '1/' > > > > Exclude all /proc/PID except /proc/1. > > > > Signed-off-by: Tobin C. Harding <me@tobin.cc> > > --- > > scripts/leaking_addresses.pl | 11 +++++++++++ > > 1 file changed, 11 insertions(+) > > > > diff --git a/scripts/leaking_addresses.pl b/scripts/leaking_addresses.pl > > index 6e5bc57caeaa..fb40e2828f43 100755 > > --- a/scripts/leaking_addresses.pl > > +++ b/scripts/leaking_addresses.pl > > @@ -10,6 +10,14 @@ > > # Use --debug to output path before parsing, this is useful to find files that > > # cause the script to choke. > > > > +# > > +# When the system is idle it is likely that most files under /proc/PID will be > > +# identical for various processes. Scanning _all_ the PIDs under /proc is > > +# unnecessary and implies that we are thoroughly scanning /proc. This is _not_ > > +# the case because there may be ways userspace can trigger creation of /proc > > +# files that leak addresses but were not present during a scan. For these two > > +# reasons we exclude all PID directories under /proc except '1/' > > + > > use warnings; > > use strict; > > use POSIX; > > @@ -472,6 +480,9 @@ sub walk > > my $path = "$pwd/$file"; > > next if (-l $path); > > > > + # skip /proc/PID except /proc/1 > > + next if ($path =~ /\/proc\/(?:[2-9][0-9]*|1[0-9]+)/); > > Can't we just do, > > substr($path, 0, len("/proc/1/")) eq "/proc/1/" ? > > seems much easier to read than the regex. This is much better. I guess it's true what they say, be careful after reading a book about hammers, everything will look like a nail. Tobin
On Tue, Feb 27, 2018 at 6:45 AM, Tobin C. Harding <me@tobin.cc> wrote: > When the system is idle it is likely that most files under /proc/PID > will be identical for various processes. Scanning _all_ the PIDs under > /proc is unnecessary and implies that we are thoroughly scanning /proc. > This is _not_ the case because there may be ways userspace can trigger > creation of /proc files that leak addresses but were not present during > a scan. For these two reasons we should exclude all PID directories > under /proc except '1/' > > Exclude all /proc/PID except /proc/1. > > Signed-off-by: Tobin C. Harding <me@tobin.cc> > --- > scripts/leaking_addresses.pl | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/scripts/leaking_addresses.pl b/scripts/leaking_addresses.pl > index 6e5bc57caeaa..fb40e2828f43 100755 > --- a/scripts/leaking_addresses.pl > +++ b/scripts/leaking_addresses.pl > @@ -10,6 +10,14 @@ > # Use --debug to output path before parsing, this is useful to find files that > # cause the script to choke. > > +# > +# When the system is idle it is likely that most files under /proc/PID will be > +# identical for various processes. Scanning _all_ the PIDs under /proc is > +# unnecessary and implies that we are thoroughly scanning /proc. This is _not_ > +# the case because there may be ways userspace can trigger creation of /proc > +# files that leak addresses but were not present during a scan. For these two > +# reasons we exclude all PID directories under /proc except '1/' > + > use warnings; > use strict; > use POSIX; > @@ -472,6 +480,9 @@ sub walk > my $path = "$pwd/$file"; > next if (-l $path); > > + # skip /proc/PID except /proc/1 > + next if ($path =~ /\/proc\/(?:[2-9][0-9]*|1[0-9]+)/); > + > next if (skip($path)); > > if (-d $path) { > -- > 2.7.4 > Would something like this do the trick? perl -e 'foreach my $dir (`ls -d /proc/[0-9]*`){next if($dir !~ "/proc/1\$"); print $dir}' /proc/1
On Tue, Feb 27, 2018 at 09:15:03AM +0200, Alexander Kapshuk wrote: > On Tue, Feb 27, 2018 at 6:45 AM, Tobin C. Harding <me@tobin.cc> wrote: > > When the system is idle it is likely that most files under /proc/PID > > will be identical for various processes. Scanning _all_ the PIDs under > > /proc is unnecessary and implies that we are thoroughly scanning /proc. > > This is _not_ the case because there may be ways userspace can trigger > > creation of /proc files that leak addresses but were not present during > > a scan. For these two reasons we should exclude all PID directories > > under /proc except '1/' > > > > Exclude all /proc/PID except /proc/1. > > > > Signed-off-by: Tobin C. Harding <me@tobin.cc> > > --- > > scripts/leaking_addresses.pl | 11 +++++++++++ > > 1 file changed, 11 insertions(+) > > > > diff --git a/scripts/leaking_addresses.pl b/scripts/leaking_addresses.pl > > index 6e5bc57caeaa..fb40e2828f43 100755 > > --- a/scripts/leaking_addresses.pl > > +++ b/scripts/leaking_addresses.pl > > @@ -10,6 +10,14 @@ > > # Use --debug to output path before parsing, this is useful to find files that > > # cause the script to choke. > > > > +# > > +# When the system is idle it is likely that most files under /proc/PID will be > > +# identical for various processes. Scanning _all_ the PIDs under /proc is > > +# unnecessary and implies that we are thoroughly scanning /proc. This is _not_ > > +# the case because there may be ways userspace can trigger creation of /proc > > +# files that leak addresses but were not present during a scan. For these two > > +# reasons we exclude all PID directories under /proc except '1/' > > + > > use warnings; > > use strict; > > use POSIX; > > @@ -472,6 +480,9 @@ sub walk > > my $path = "$pwd/$file"; > > next if (-l $path); > > > > + # skip /proc/PID except /proc/1 > > + next if ($path =~ /\/proc\/(?:[2-9][0-9]*|1[0-9]+)/); > > + > > next if (skip($path)); > > > > if (-d $path) { > > -- > > 2.7.4 > > > > Would something like this do the trick? > perl -e 'foreach my $dir (`ls -d /proc/[0-9]*`){next if($dir !~ > "/proc/1\$"); print $dir}' > /proc/1 thanks for the suggestion Alexander. Here is Tycho's suggestion (from other email, copied here for reference: > substr($path, 0, len("/proc/1/")) eq "/proc/1/" I originally thought Tycho's suggestion was correct until I read yours and realized that they both find '/proc/1'. You filter on the numbered directories for '/proc/1' (missing the other directories) and Tycho finds only directories with '/proc/1' as the leading characters. Both of these differ to the original regex in that the original skips numbered directories (under '/proc') that are _not_ '/proc/1' i.e it allows parsing of all the non-numbered directories and parsing of '/proc/1'. If my reasoning is correct, perhaps we have at least shown that that the regex should have a comment :) Happy to be corrected. thanks, Tobin.
On Tue, Feb 27, 2018 at 03:45:09PM +1100, Tobin C. Harding wrote: > When the system is idle it is likely that most files under /proc/PID > will be identical for various processes. Scanning _all_ the PIDs under > /proc is unnecessary and implies that we are thoroughly scanning /proc. > This is _not_ the case because there may be ways userspace can trigger > creation of /proc files that leak addresses but were not present during > a scan. For these two reasons we should exclude all PID directories > under /proc except '1/' > > Exclude all /proc/PID except /proc/1. > > Signed-off-by: Tobin C. Harding <me@tobin.cc> > --- > scripts/leaking_addresses.pl | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/scripts/leaking_addresses.pl b/scripts/leaking_addresses.pl > index 6e5bc57caeaa..fb40e2828f43 100755 > --- a/scripts/leaking_addresses.pl > +++ b/scripts/leaking_addresses.pl > @@ -10,6 +10,14 @@ > # Use --debug to output path before parsing, this is useful to find files that > # cause the script to choke. > > +# > +# When the system is idle it is likely that most files under /proc/PID will be > +# identical for various processes. Scanning _all_ the PIDs under /proc is > +# unnecessary and implies that we are thoroughly scanning /proc. This is _not_ > +# the case because there may be ways userspace can trigger creation of /proc > +# files that leak addresses but were not present during a scan. For these two > +# reasons we exclude all PID directories under /proc except '1/' > + > use warnings; > use strict; > use POSIX; > @@ -472,6 +480,9 @@ sub walk > my $path = "$pwd/$file"; > next if (-l $path); > > + # skip /proc/PID except /proc/1 > + next if ($path =~ /\/proc\/(?:[2-9][0-9]*|1[0-9]+)/); Perhaps the intent of this is clearer? next if (($path =~ /^\/proc\/[0-9]+$/) && ($path !~ /^\/proc\/1$/)); thanks, Tobin.
On Fri, Mar 02, 2018 at 08:06:23AM +1100, Tobin C. Harding wrote: > On Tue, Feb 27, 2018 at 03:45:09PM +1100, Tobin C. Harding wrote: > > When the system is idle it is likely that most files under /proc/PID > > will be identical for various processes. Scanning _all_ the PIDs under > > /proc is unnecessary and implies that we are thoroughly scanning /proc. > > This is _not_ the case because there may be ways userspace can trigger > > creation of /proc files that leak addresses but were not present during > > a scan. For these two reasons we should exclude all PID directories > > under /proc except '1/' > > > > Exclude all /proc/PID except /proc/1. > > > > Signed-off-by: Tobin C. Harding <me@tobin.cc> > > --- > > scripts/leaking_addresses.pl | 11 +++++++++++ > > 1 file changed, 11 insertions(+) > > > > diff --git a/scripts/leaking_addresses.pl b/scripts/leaking_addresses.pl > > index 6e5bc57caeaa..fb40e2828f43 100755 > > --- a/scripts/leaking_addresses.pl > > +++ b/scripts/leaking_addresses.pl > > @@ -10,6 +10,14 @@ > > # Use --debug to output path before parsing, this is useful to find files that > > # cause the script to choke. > > > > +# > > +# When the system is idle it is likely that most files under /proc/PID will be > > +# identical for various processes. Scanning _all_ the PIDs under /proc is > > +# unnecessary and implies that we are thoroughly scanning /proc. This is _not_ > > +# the case because there may be ways userspace can trigger creation of /proc > > +# files that leak addresses but were not present during a scan. For these two > > +# reasons we exclude all PID directories under /proc except '1/' > > + > > use warnings; > > use strict; > > use POSIX; > > @@ -472,6 +480,9 @@ sub walk > > my $path = "$pwd/$file"; > > next if (-l $path); > > > > + # skip /proc/PID except /proc/1 > > + next if ($path =~ /\/proc\/(?:[2-9][0-9]*|1[0-9]+)/); > > Perhaps the intent of this is clearer? > > next if (($path =~ /^\/proc\/[0-9]+$/) && > ($path !~ /^\/proc\/1$/)); +1, works for me. Cheers, Tycho
On Thu, Mar 1, 2018 at 11:06 PM, Tobin C. Harding <me@tobin.cc> wrote: > On Tue, Feb 27, 2018 at 03:45:09PM +1100, Tobin C. Harding wrote: >> When the system is idle it is likely that most files under /proc/PID >> will be identical for various processes. Scanning _all_ the PIDs under >> /proc is unnecessary and implies that we are thoroughly scanning /proc. >> This is _not_ the case because there may be ways userspace can trigger >> creation of /proc files that leak addresses but were not present during >> a scan. For these two reasons we should exclude all PID directories >> under /proc except '1/' >> >> Exclude all /proc/PID except /proc/1. >> >> Signed-off-by: Tobin C. Harding <me@tobin.cc> >> --- >> scripts/leaking_addresses.pl | 11 +++++++++++ >> 1 file changed, 11 insertions(+) >> >> diff --git a/scripts/leaking_addresses.pl b/scripts/leaking_addresses.pl >> index 6e5bc57caeaa..fb40e2828f43 100755 >> --- a/scripts/leaking_addresses.pl >> +++ b/scripts/leaking_addresses.pl >> @@ -10,6 +10,14 @@ >> # Use --debug to output path before parsing, this is useful to find files that >> # cause the script to choke. >> >> +# >> +# When the system is idle it is likely that most files under /proc/PID will be >> +# identical for various processes. Scanning _all_ the PIDs under /proc is >> +# unnecessary and implies that we are thoroughly scanning /proc. This is _not_ >> +# the case because there may be ways userspace can trigger creation of /proc >> +# files that leak addresses but were not present during a scan. For these two >> +# reasons we exclude all PID directories under /proc except '1/' >> + >> use warnings; >> use strict; >> use POSIX; >> @@ -472,6 +480,9 @@ sub walk >> my $path = "$pwd/$file"; >> next if (-l $path); >> >> + # skip /proc/PID except /proc/1 >> + next if ($path =~ /\/proc\/(?:[2-9][0-9]*|1[0-9]+)/); > > Perhaps the intent of this is clearer? > > next if (($path =~ /^\/proc\/[0-9]+$/) && > ($path !~ /^\/proc\/1$/)); > > > thanks, > Tobin. Hi Tobin, The intent is crystal clear now. Thanks. Here's something that generates the same output as the code above: next if ($path !~ "^/proc/(1|[^0-9]+)\$"); I'm not insisting this be given any preference whatsoever. Thanks.
diff --git a/scripts/leaking_addresses.pl b/scripts/leaking_addresses.pl index 6e5bc57caeaa..fb40e2828f43 100755 --- a/scripts/leaking_addresses.pl +++ b/scripts/leaking_addresses.pl @@ -10,6 +10,14 @@ # Use --debug to output path before parsing, this is useful to find files that # cause the script to choke. +# +# When the system is idle it is likely that most files under /proc/PID will be +# identical for various processes. Scanning _all_ the PIDs under /proc is +# unnecessary and implies that we are thoroughly scanning /proc. This is _not_ +# the case because there may be ways userspace can trigger creation of /proc +# files that leak addresses but were not present during a scan. For these two +# reasons we exclude all PID directories under /proc except '1/' + use warnings; use strict; use POSIX; @@ -472,6 +480,9 @@ sub walk my $path = "$pwd/$file"; next if (-l $path); + # skip /proc/PID except /proc/1 + next if ($path =~ /\/proc\/(?:[2-9][0-9]*|1[0-9]+)/); + next if (skip($path)); if (-d $path) {
When the system is idle it is likely that most files under /proc/PID will be identical for various processes. Scanning _all_ the PIDs under /proc is unnecessary and implies that we are thoroughly scanning /proc. This is _not_ the case because there may be ways userspace can trigger creation of /proc files that leak addresses but were not present during a scan. For these two reasons we should exclude all PID directories under /proc except '1/' Exclude all /proc/PID except /proc/1. Signed-off-by: Tobin C. Harding <me@tobin.cc> --- scripts/leaking_addresses.pl | 11 +++++++++++ 1 file changed, 11 insertions(+)