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s390: fix test_fp_ctl inline assembly contraints

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The test_fp_ctl function is used to test if a given value is a valid
floating-point control. The inline assembly in test_fp_ctl uses an
incorrect constraint for the 'orig_fpc' variable. If the compiler
chooses the same register for 'fpc' and 'orig_fpc' the test_fp_ctl()
function always returns true. This allows user space to trigger
kernel oopses with invalid floating-point control values on the
signal stack.

This problem has been introduced with git commit 4725c86055
"s390: fix save and restore of the floating-point-control register"

Cc: stable@vger.kernel.org # v3.13+
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Martin Schwidefsky 2016-06-27 17:06:45 +02:00
parent 5419447e21
commit bcf4dd5f9e
1 changed files with 1 additions and 1 deletions
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2
arch/s390/include/asm/fpu/api.h
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@ -22,7 +22,7 @@ static inline int test_fp_ctl(u32 fpc)
" la %0,0\n"
"1:\n"
EX_TABLE(0b,1b)
: "=d" (rc), "=d" (orig_fpc)
: "=d" (rc), "=&d" (orig_fpc)
: "d" (fpc), "0" (-EINVAL));
return rc;
}