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s390/cpum_sf.c: fix file permission for cpum_sfb_size 

commit 78d732e1f3 upstream.

This file is installed by the s390 CPU Measurement sampling
facility device driver to export supported minimum and
maximum sample buffer sizes.
This file is read by lscpumf tool to display the details
of the device driver capabilities. The lscpumf tool might
be invoked by a non-root user. In this case it does not
print anything because the file contents can not be read.

Fix this by allowing read access for all users. Reading
the file contents is ok, changing the file contents is
left to the root user only.

For further reference and details see:
 [1] https://github.com/ibm-s390-tools/s390-tools/issues/97

Fixes: 69f239ed33 ("s390/cpum_sf: Dynamically extend the sampling buffer if overflows occur")
Cc: <stable@vger.kernel.org> # 3.14
Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Acked-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
5.4-rM2-2.2.x-imx-squashed
Thomas Richter 2020-11-11 16:26:25 +01:00 committed by Greg Kroah-Hartman
parent 89d73a97af
commit e6e76a26fd
1 changed files with 1 additions and 1 deletions
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2
arch/s390/kernel/perf_cpum_sf.c
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@ -2217,4 +2217,4 @@ out:
}
arch_initcall(init_cpum_sampling_pmu);
core_param(cpum_sfb_size, CPUM_SF_MAX_SDB, sfb_size, 0640);
core_param(cpum_sfb_size, CPUM_SF_MAX_SDB, sfb_size, 0644);