Messages in this thread Patch in this message | | | From | Mathieu Poirier <> | Date | Wed, 14 Aug 2019 12:04:33 -0600 | Subject | Re: [PATCH v3 3/4] perf: Use CAP_SYSLOG with kptr_restrict checks |
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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.
> if (r != NULL) { > @@ -2190,9 +2197,9 @@ static bool symbol__read_kptr_restrict(void) > char line[8]; > > if (fgets(line, sizeof(line), fp) != NULL) > - value = ((geteuid() != 0) || (getuid() != 0)) ? > - (atoi(line) != 0) : > - (atoi(line) == 2); > + value = perf_cap__capable(CAP_SYSLOG) ? > + (atoi(line) >= 2) : > + (atoi(line) != 0); > > fclose(fp); > } > -- > 2.7.4 >
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