Messages in this thread | | | From | Arnaldo Carvalho de Melo <> | Date | Wed, 14 Aug 2019 15:48:14 -0300 | Subject | Re: [PATCH v3 3/4] perf: Use CAP_SYSLOG with kptr_restrict checks |
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Em Wed, Aug 14, 2019 at 12:04:33PM -0600, Mathieu Poirier escreveu: > On Wed, 7 Aug 2019 at 08:44, Igor Lubashev <ilubashe@akamai.com> wrote: > > > > Kernel is using CAP_SYSLOG capability instead of uid==0 and euid==0 when > > checking kptr_restrict. Make perf do the same. > > > > Also, the kernel is a more restrictive than "no restrictions" in case of > > kptr_restrict==0, so add the same logic to perf. > > > > Signed-off-by: Igor Lubashev <ilubashe@akamai.com> > > --- > > tools/perf/util/symbol.c | 15 +++++++++++---- > > 1 file changed, 11 insertions(+), 4 deletions(-) > > > > diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c > > index 173f3378aaa0..046271103499 100644 > > --- a/tools/perf/util/symbol.c > > +++ b/tools/perf/util/symbol.c > > @@ -4,6 +4,7 @@ > > #include <stdlib.h> > > #include <stdio.h> > > #include <string.h> > > +#include <linux/capability.h> > > #include <linux/kernel.h> > > #include <linux/mman.h> > > #include <linux/time64.h> > > @@ -15,8 +16,10 @@ > > #include <inttypes.h> > > #include "annotate.h" > > #include "build-id.h" > > +#include "cap.h" > > #include "util.h" > > #include "debug.h" > > +#include "event.h" > > #include "machine.h" > > #include "map.h" > > #include "symbol.h" > > @@ -890,7 +893,11 @@ bool symbol__restricted_filename(const char *filename, > > { > > bool restricted = false; > > > > - if (symbol_conf.kptr_restrict) { > > + /* Per kernel/kallsyms.c: > > + * we also restrict when perf_event_paranoid > 1 w/o CAP_SYSLOG > > + */ > > + if (symbol_conf.kptr_restrict || > > + (perf_event_paranoid() > 1 && !perf_cap__capable(CAP_SYSLOG))) { > > char *r = realpath(filename, NULL); > > > > # echo 0 > /proc/sys/kernel/kptr_restrict > # ./tools/perf/perf record -e instructions:k uname > perf: Segmentation fault > Obtained 10 stack frames. > ./tools/perf/perf(sighandler_dump_stack+0x44) [0x55af9e5da5d4] > /lib/x86_64-linux-gnu/libc.so.6(+0x3ef20) [0x7fd31efb6f20] > ./tools/perf/perf(perf_event__synthesize_kernel_mmap+0xa7) [0x55af9e590337] > ./tools/perf/perf(+0x1cf5be) [0x55af9e50c5be] > ./tools/perf/perf(cmd_record+0x1022) [0x55af9e50dff2] > ./tools/perf/perf(+0x23f98d) [0x55af9e57c98d] > ./tools/perf/perf(+0x23fc9e) [0x55af9e57cc9e] > ./tools/perf/perf(main+0x369) [0x55af9e4f6bc9] > /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xe7) [0x7fd31ef99b97] > ./tools/perf/perf(_start+0x2a) [0x55af9e4f704a] > Segmentation fault > > I can reproduce this on both x86 and ARM64.
I don't see this with these two csets removed:
7ff5b5911144 perf symbols: Use CAP_SYSLOG with kptr_restrict checks d7604b66102e perf tools: Use CAP_SYS_ADMIN with perf_event_paranoid checks
Which were the ones I guessed were related to the problem you reported, so they are out of my ongoing perf/core pull request to Ingo/Thomas, now trying with these applied and your instructions...
- Arnaldo
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