powerpc/pkeys: key allocation/deallocation must not change pkey registers

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Key allocation and deallocation has the side effect of programming the
UAMOR/AMR/IAMR registers. This is wrong, since its the responsibility of
the application and not that of the kernel, to modify the permission on
the key.

Do not modify the pkey registers at key allocation/deallocation.

This patch also fixes a bug where a sys_pkey_free() resets the UAMOR
bits of the key, thus making its permissions unmodifiable from user
space. Later if the same key gets reallocated from a different thread
this thread will no longer be able to change the permissions on the key.

Fixes: cf43d3b264 ("powerpc: Enable pkey subsystem")
Cc: stable@vger.kernel.org # v4.16+
Reviewed-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Signed-off-by: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

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This commit is contained in:

Ram Pai 2018-07-17 06:51:04 -07:00 • committed by Michael Ellerman

parent de113256f8

commit 4a4a5e5d2a

2 changed files with 0 additions and 38 deletions

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11

arch/powerpc/include/asm/pkeys.h

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27

arch/powerpc/mm/pkeys.c

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