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| author | Noah Goldstein <goldstein.w.n@gmail.com> | 2022-09-20 17:58:04 -0700 |
|---|---|---|
| committer | Noah Goldstein <goldstein.w.n@gmail.com> | 2022-09-28 20:15:16 -0700 |
| commit | b0969fa53a28b4ab2159806bf6c99a98999502ee (patch) | |
| tree | 8aafe93540ffbf58be6b57e5ea5e71ba3fc5c030 /sysdeps | |
| parent | 3e5760fcb48528d48deeb60cb885a97bb731160c (diff) | |
| download | glibc-b0969fa53a28b4ab2159806bf6c99a98999502ee.zip glibc-b0969fa53a28b4ab2159806bf6c99a98999502ee.tar.gz glibc-b0969fa53a28b4ab2159806bf6c99a98999502ee.tar.bz2 | |
x86: Fix wcsnlen-avx2 page cross length comparison [BZ #29591]
Previous implementation was adjusting length (rsi) to match
bytes (eax), but since there is no bound to length this can cause
overflow.
Fix is to just convert the byte-count (eax) to length by dividing by
sizeof (wchar_t) before the comparison.
Full check passes on x86-64 and build succeeds w/ and w/o multiarch.
Diffstat (limited to 'sysdeps')
| -rw-r--r-- | sysdeps/x86_64/multiarch/strlen-avx2.S | 7 |
1 files changed, 2 insertions, 5 deletions
diff --git a/sysdeps/x86_64/multiarch/strlen-avx2.S b/sysdeps/x86_64/multiarch/strlen-avx2.S index 0593fb3..b9b58ef 100644 --- a/sysdeps/x86_64/multiarch/strlen-avx2.S +++ b/sysdeps/x86_64/multiarch/strlen-avx2.S @@ -544,14 +544,11 @@ L(return_vzeroupper): L(cross_page_less_vec): tzcntl %eax, %eax # ifdef USE_AS_WCSLEN - /* NB: Multiply length by 4 to get byte count. */ - sall $2, %esi + /* NB: Divide by 4 to convert from byte-count to length. */ + shrl $2, %eax # endif cmpq %rax, %rsi cmovb %esi, %eax -# ifdef USE_AS_WCSLEN - shrl $2, %eax -# endif VZEROUPPER_RETURN # endif |