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author | Joseph Myers <joseph@codesourcery.com> | 2020-02-12 23:31:56 +0000 |
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committer | Joseph Myers <joseph@codesourcery.com> | 2020-02-12 23:31:56 +0000 |
commit | 9333498794cde1d5cca518badf79533a24114b6f (patch) | |
tree | 19e5d0d11573074dd2a21f5bf87fc31f94bbced3 /nss/tst-nss-test4.c | |
parent | 4fbba6fe904d0094ddc4284066b3860d119cbd4a (diff) | |
download | glibc-9333498794cde1d5cca518badf79533a24114b6f.tar.gz glibc-9333498794cde1d5cca518badf79533a24114b6f.tar.xz glibc-9333498794cde1d5cca518badf79533a24114b6f.zip |
Avoid ldbl-96 stack corruption from range reduction of pseudo-zero (bug 25487).
Bug 25487 reports stack corruption in ldbl-96 sinl on a pseudo-zero argument (an representation where all the significand bits, including the explicit high bit, are zero, but the exponent is not zero, which is not a valid representation for the long double type). Although this is not a valid long double representation, existing practice in this area (see bug 4586, originally marked invalid but subsequently fixed) is that we still seek to avoid invalid memory accesses as a result, in case of programs that treat arbitrary binary data as long double representations, although the invalid representations of the ldbl-96 format do not need to be consistently handled the same as any particular valid representation. This patch makes the range reduction detect pseudo-zero and unnormal representations that would otherwise go to __kernel_rem_pio2, and returns a NaN for them instead of continuing with the range reduction process. (Pseudo-zero and unnormal representations whose unbiased exponent is less than -1 have already been safely returned from the function before this point without going through the rest of range reduction.) Pseudo-zero representations would previously result in the value passed to __kernel_rem_pio2 being all-zero, which is definitely unsafe; unnormal representations would previously result in a value passed whose high bit is zero, which might well be unsafe since that is not a form of input expected by __kernel_rem_pio2. Tested for x86_64.
Diffstat (limited to 'nss/tst-nss-test4.c')
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