linux/tools
Wang Nan 3dbe46c524 perf record: Fix segfault when running with suid and kptr_restrict is 1
Before this patch perf panics if kptr_restrict is set to 1 and perf is
owned by root with suid set:

  $ whoami
  wangnan
  $ ls -l ./perf
  -rwsr-xr-x 1 root root 19781908 Sep 21 19:29 /home/wangnan/perf
  $ cat /proc/sys/kernel/kptr_restrict
  1
  $ cat /proc/sys/kernel/perf_event_paranoid
  -1
  $ ./perf record -a
  Segmentation fault (core dumped)
  $

The reason is that perf assumes it is allowed to read kptr from
/proc/kallsyms when euid is root, but in fact the kernel doesn't allow
reading kptr when euid and uid do not match with each other:

  $ cp /bin/cat .
  $ sudo chown root:root ./cat
  $ sudo chmod u+s ./cat
  $ cat /proc/kallsyms | grep do_fork
  0000000000000000 T _do_fork          <--- kptr is hidden even euid is root
  $ sudo cat /proc/kallsyms | grep do_fork
  ffffffff81080230 T _do_fork

See lib/vsprintf.c for kernel side code.

This patch fixes this problem by checking both uid and euid.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexei Starovoitov <ast@fb.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/20161115040617.69788-3-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2016-11-25 11:11:10 -03:00
..
accounting tools: move accounting tool from Documentation 2016-09-23 13:07:15 -06:00
arch x86/cpufeature: Add AVX512_4VNNIW and AVX512_4FMAPS features 2016-10-19 17:37:13 +02:00
build tools build: Add jvmti feature detection support 2016-11-14 12:40:32 -03:00
cgroup
firewire
gpio
hv Drivers: hv: utils: Check VSS daemon is listening before a hot backup 2016-09-02 17:22:51 +02:00
iio Second set of iio new device support, features and cleanups for the 4.9 cycle. 2016-09-14 20:42:03 +02:00
include tools: Update asm-generic/mman-common.h copy from the kernel 2016-10-28 11:29:43 -02:00
kvm/kvm_stat
laptop tools: move laptops dslm tool from Documentation 2016-09-23 13:07:21 -06:00
lguest tools/lguest: Don't bork the terminal in case of wrong args 2016-09-08 08:05:24 +02:00
lib tools lib traceevent: Add retrieval of preempt count and latency flags 2016-11-23 10:44:03 -03:00
net
nfsd
objtool objtool: Fix rare switch jump table pattern detection 2016-10-27 08:20:27 +02:00
pcmcia tools: move pcmcia crc32hash tool from Documentation 2016-09-23 13:07:27 -06:00
perf perf record: Fix segfault when running with suid and kptr_restrict is 1 2016-11-25 11:11:10 -03:00
power tools/power/acpi: Remove direct kernel source include reference 2016-11-16 22:31:26 +01:00
scripts
spi Merge remote-tracking branches 'spi/topic/ti-qspi', 'spi/topic/tools', 'spi/topic/txx9' and 'spi/topic/xlp' into spi-next 2016-09-30 09:14:22 -07:00
testing linux-kselftest-4.9-rc1-update 2016-10-14 15:17:12 -07:00
thermal/tmon
time
usb
virtio ringtest: poll for new buffers once before updating event index 2016-10-31 00:21:43 +02:00
vm
Makefile