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* [glibc] x86: Fix strncat-avx2.S reading past length [BZ #30065]
@ 2023-02-01 1:14 Noah Goldstein
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From: Noah Goldstein @ 2023-02-01 1:14 UTC (permalink / raw)
To: glibc-cvs
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=b2c474f8de4c92bfe7435853a96805ec32d68dfa
commit b2c474f8de4c92bfe7435853a96805ec32d68dfa
Author: Noah Goldstein <goldstein.w.n@gmail.com>
Date: Tue Jan 31 17:46:56 2023 -0600
x86: Fix strncat-avx2.S reading past length [BZ #30065]
Occurs when `src` has no null-term.
Two cases:
1) Zero-length check is doing:
```
test %rdx, %rdx
jl L(zero_len)
```
which doesn't actually check zero (was at some point `decq` and the
flag never got updated).
The fix is just make the flag `jle` i.e:
```
test %rdx, %rdx
jle L(zero_len)
```
2) Length check in page-cross case checking if we should continue is
doing:
```
cmpq %r8, %rdx
jb L(page_cross_small)
```
which means we will continue searching for null-term if length ends at
the end of a page and there was no null-term in `src`.
The fix is to make the flag:
```
cmpq %r8, %rdx
jbe L(page_cross_small)
```
Diff:
---
string/test-strncat.c | 25 ++++++++++++++++++++++++-
sysdeps/x86_64/multiarch/strncat-avx2.S | 4 ++--
2 files changed, 26 insertions(+), 3 deletions(-)
diff --git a/string/test-strncat.c b/string/test-strncat.c
index e03d329e1c..c0cde206ee 100644
--- a/string/test-strncat.c
+++ b/string/test-strncat.c
@@ -28,6 +28,7 @@
# define CHAR char
# define UCHAR unsigned char
# define SIMPLE_STRNCAT simple_strncat
+# define STRNLEN strnlen
# define STRLEN strlen
# define MEMSET memset
# define MEMCPY memcpy
@@ -40,6 +41,7 @@
# define CHAR wchar_t
# define UCHAR wchar_t
# define SIMPLE_STRNCAT simple_wcsncat
+# define STRNLEN wcsnlen
# define STRLEN wcslen
# define MEMSET wmemset
# define MEMCPY wmemcpy
@@ -78,7 +80,7 @@ do_one_test (impl_t *impl, CHAR *dst, const CHAR *src, size_t n)
return;
}
- size_t len = STRLEN (src);
+ size_t len = STRNLEN (src, n);
if (MEMCMP (dst + k, src, len + 1 > n ? n : len + 1) != 0)
{
error (0, 0, "Incorrect concatenation in function %s",
@@ -95,6 +97,26 @@ do_one_test (impl_t *impl, CHAR *dst, const CHAR *src, size_t n)
}
}
+static void
+do_test_src_no_nullterm_bz30065 (void)
+{
+ /* NB: "src does not need to be null-terminated if it contains n or more
+ * bytes." */
+ CHAR *s1, *s2;
+ size_t bound = page_size / sizeof (CHAR);
+ s1 = (CHAR *) (buf1 + BUF1PAGES * page_size);
+ s2 = (CHAR *) buf2;
+ MEMSET (s1 - bound, -1, bound);
+ for (size_t n = 0; n < bound; ++n)
+ {
+ FOR_EACH_IMPL (impl, 0)
+ {
+ s2[0] = '\0';
+ do_one_test (impl, s2, s1 - n, n);
+ }
+ }
+}
+
static void
do_test (size_t align1, size_t align2, size_t len1, size_t len2,
size_t n, int max_char)
@@ -372,6 +394,7 @@ test_main (void)
do_random_tests ();
do_overflow_tests ();
+ do_test_src_no_nullterm_bz30065 ();
return ret;
}
diff --git a/sysdeps/x86_64/multiarch/strncat-avx2.S b/sysdeps/x86_64/multiarch/strncat-avx2.S
index b380e8e11c..c2ff202238 100644
--- a/sysdeps/x86_64/multiarch/strncat-avx2.S
+++ b/sysdeps/x86_64/multiarch/strncat-avx2.S
@@ -66,7 +66,7 @@ ENTRY(STRNCAT)
salq $2, %rdx
# else
test %rdx, %rdx
- jl L(zero_len)
+ jle L(zero_len)
# endif
vpxor %VZERO_128, %VZERO_128, %VZERO_128
@@ -387,7 +387,7 @@ L(page_cross):
subl %esi, %r8d
andl $(VEC_SIZE - 1), %r8d
cmpq %r8, %rdx
- jb L(page_cross_small)
+ jbe L(page_cross_small)
/* Optimizing more aggressively for space as this is very cold
code. This saves 2x cache lines. */
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2023-02-01 1:14 [glibc] x86: Fix strncat-avx2.S reading past length [BZ #30065] Noah Goldstein
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