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CVE-2012-3406: Stack overflow in vfprintf [BZ #16617]
A larger number of format specifiers coudld cause a stack overflow, potentially allowing to bypass _FORTIFY_SOURCE format string protection.
This commit is contained in:
Jeff Law
Florian Weimer
parent
3a12c70f13
commit
a5357b7ce2
@ -1,3 +1,12 @@
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2014-12-15 Jeff Law <law@redhat.com>
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[BZ #16617]
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* stdio-common/vfprintf.c (vfprintf): Allocate large specs array
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on the heap. (CVE-2012-3406)
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* stdio-common/bug23-2.c, stdio-common/bug23-3.c: New file.
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* stdio-common/bug23-4.c: New file. Test case by Joseph Myers.
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* stdio-common/Makefile (tests): Add bug23-2, bug23-3, bug23-4.
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2014-12-15 Will Newton <will.newton@linaro.org>
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* manual/install.texi: Bump required version of texinfo
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13
NEWS
13
NEWS
@ -10,11 +10,11 @@ Version 2.21
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* The following bugs are resolved with this release:
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6652, 10672, 12847, 12926, 13862, 14132, 14138, 14171, 14498, 15215,
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15884, 16469, 16619, 16657, 16740, 16857, 17192, 17266, 17344, 17363,
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17370, 17371, 17411, 17460, 17475, 17485, 17501, 17506, 17508, 17522,
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17555, 17570, 17571, 17572, 17573, 17574, 17581, 17582, 17583, 17584,
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17585, 17589, 17594, 17601, 17608, 17616, 17625, 17633, 17634, 17647,
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17653, 17664, 17665, 17668, 17682.
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15884, 16469, 16617, 16619, 16657, 16740, 16857, 17192, 17266, 17344,
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17363, 17370, 17371, 17411, 17460, 17475, 17485, 17501, 17506, 17508,
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17522, 17555, 17570, 17571, 17572, 17573, 17574, 17581, 17582, 17583,
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17584, 17585, 17589, 17594, 17601, 17608, 17616, 17625, 17633, 17634,
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17647, 17653, 17664, 17665, 17668, 17682.
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* CVE-2104-7817 The wordexp function could ignore the WRDE_NOCMD flag
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under certain input conditions resulting in the execution of a shell for
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@ -22,6 +22,9 @@ Version 2.21
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implementation now checks WRDE_NOCMD immediately before executing the
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shell and returns the error WRDE_CMDSUB as expected.
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* CVE-2012-3406 printf-style functions could run into a stack overflow when
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processing format strings with a large number of format specifiers.
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* The minimum GCC version that can be used to build this version of the GNU
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C Library is GCC 4.6. Older GCC versions, and non-GNU compilers, can
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still be used to compile programs using the GNU C Library.
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@ -57,7 +57,7 @@ tests := tstscanf test_rdwr test-popen tstgetln test-fseek \
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bug19 bug19a tst-popen2 scanf13 scanf14 scanf15 bug20 bug21 bug22 \
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scanf16 scanf17 tst-setvbuf1 tst-grouping bug23 bug24 \
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bug-vfprintf-nargs tst-long-dbl-fphex tst-fphex-wide tst-sprintf3 \
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bug25 tst-printf-round bug26
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bug25 tst-printf-round bug23-2 bug23-3 bug23-4
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test-srcs = tst-unbputc tst-printf
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70
stdio-common/bug23-2.c
Normal file
70
stdio-common/bug23-2.c
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@ -0,0 +1,70 @@
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#include <stdio.h>
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#include <string.h>
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#include <stdlib.h>
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static const char expected[] = "\
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\n\
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a\n\
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abbcd55\
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\n\
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a\n\
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abbcd55\
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\n\
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a\n\
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abbcd55\
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\n\
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a\n\
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abbcd55\
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\n\
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a\n\
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abbcd55\
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\n\
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a\n\
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abbcd55\
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\n\
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a\n\
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abbcd55\
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\n\
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a\n\
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abbcd55\
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\n\
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a\n\
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abbcd55\
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\n\
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a\n\
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abbcd55\
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\n\
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a\n\
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abbcd55\
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\n\
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a\n\
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abbcd55\
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\n\
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a\n\
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abbcd55%%%%%%%%%%%%%%%%%%%%%%%%%%\n";
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static int
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do_test (void)
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{
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char *buf = malloc (strlen (expected) + 1);
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snprintf (buf, strlen (expected) + 1,
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"\n%1$s\n" "%1$s" "%2$s" "%2$s" "%3$s" "%4$s" "%5$d" "%5$d"
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"\n%1$s\n" "%1$s" "%2$s" "%2$s" "%3$s" "%4$s" "%5$d" "%5$d"
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"\n%1$s\n" "%1$s" "%2$s" "%2$s" "%3$s" "%4$s" "%5$d" "%5$d"
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"\n%1$s\n" "%1$s" "%2$s" "%2$s" "%3$s" "%4$s" "%5$d" "%5$d"
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"\n%1$s\n" "%1$s" "%2$s" "%2$s" "%3$s" "%4$s" "%5$d" "%5$d"
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"\n%1$s\n" "%1$s" "%2$s" "%2$s" "%3$s" "%4$s" "%5$d" "%5$d"
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"\n%1$s\n" "%1$s" "%2$s" "%2$s" "%3$s" "%4$s" "%5$d" "%5$d"
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"\n%1$s\n" "%1$s" "%2$s" "%2$s" "%3$s" "%4$s" "%5$d" "%5$d"
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"\n%1$s\n" "%1$s" "%2$s" "%2$s" "%3$s" "%4$s" "%5$d" "%5$d"
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"\n%1$s\n" "%1$s" "%2$s" "%2$s" "%3$s" "%4$s" "%5$d" "%5$d"
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"\n%1$s\n" "%1$s" "%2$s" "%2$s" "%3$s" "%4$s" "%5$d" "%5$d"
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"\n%1$s\n" "%1$s" "%2$s" "%2$s" "%3$s" "%4$s" "%5$d" "%5$d"
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"\n%1$s\n" "%1$s" "%2$s" "%2$s" "%3$s" "%4$s" "%5$d" "%5$d"
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"%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%\n",
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"a", "b", "c", "d", 5);
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return strcmp (buf, expected) != 0;
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}
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#define TEST_FUNCTION do_test ()
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#include "../test-skeleton.c"
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50
stdio-common/bug23-3.c
Normal file
50
stdio-common/bug23-3.c
Normal file
@ -0,0 +1,50 @@
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#include <stdio.h>
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#include <string.h>
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#include <stdlib.h>
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int
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do_test (void)
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{
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size_t instances = 16384;
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#define X0 "\n%1$s\n" "%1$s" "%2$s" "%2$s" "%3$s" "%4$s" "%5$d" "%5$d"
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const char *item = "\na\nabbcd55";
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#define X3 X0 X0 X0 X0 X0 X0 X0 X0
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#define X6 X3 X3 X3 X3 X3 X3 X3 X3
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#define X9 X6 X6 X6 X6 X6 X6 X6 X6
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#define X12 X9 X9 X9 X9 X9 X9 X9 X9
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#define X14 X12 X12 X12 X12
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#define TRAILER "%%%%%%%%%%%%%%%%%%%%%%%%%%"
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#define TRAILER2 TRAILER TRAILER
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size_t length = instances * strlen (item) + strlen (TRAILER) + 1;
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char *buf = malloc (length + 1);
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snprintf (buf, length + 1,
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X14 TRAILER2 "\n",
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"a", "b", "c", "d", 5);
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const char *p = buf;
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size_t i;
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for (i = 0; i < instances; ++i)
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{
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const char *expected;
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for (expected = item; *expected; ++expected)
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{
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if (*p != *expected)
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{
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printf ("mismatch at offset %zu (%zu): expected %d, got %d\n",
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(size_t) (p - buf), i, *expected & 0xFF, *p & 0xFF);
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return 1;
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}
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++p;
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}
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}
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if (strcmp (p, TRAILER "\n") != 0)
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{
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printf ("mismatch at trailer: [%s]\n", p);
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return 1;
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}
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free (buf);
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return 0;
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}
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#define TEST_FUNCTION do_test ()
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#include "../test-skeleton.c"
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31
stdio-common/bug23-4.c
Normal file
31
stdio-common/bug23-4.c
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/resource.h>
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#define LIMIT 1000000
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int
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main (void)
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{
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struct rlimit lim;
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getrlimit (RLIMIT_STACK, &lim);
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lim.rlim_cur = 1048576;
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setrlimit (RLIMIT_STACK, &lim);
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char *fmtstr = malloc (4 * LIMIT + 1);
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if (fmtstr == NULL)
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abort ();
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char *output = malloc (LIMIT + 1);
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if (output == NULL)
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abort ();
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for (size_t i = 0; i < LIMIT; i++)
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memcpy (fmtstr + 4 * i, "%1$d", 4);
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fmtstr[4 * LIMIT] = '\0';
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int ret = snprintf (output, LIMIT + 1, fmtstr, 0);
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if (ret != LIMIT)
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abort ();
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for (size_t i = 0; i < LIMIT; i++)
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if (output[i] != '0')
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abort ();
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return 0;
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}
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@ -263,6 +263,12 @@ vfprintf (FILE *s, const CHAR_T *format, va_list ap)
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/* For the argument descriptions, which may be allocated on the heap. */
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void *args_malloced = NULL;
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/* For positional argument handling. */
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struct printf_spec *specs;
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/* Track if we malloced the SPECS array and thus must free it. */
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bool specs_malloced = false;
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/* This table maps a character into a number representing a
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class. In each step there is a destination label for each
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class. */
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@ -1679,8 +1685,8 @@ do_positional:
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size_t nspecs = 0;
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/* A more or less arbitrary start value. */
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size_t nspecs_size = 32 * sizeof (struct printf_spec);
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struct printf_spec *specs = alloca (nspecs_size);
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specs = alloca (nspecs_size);
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/* The number of arguments the format string requests. This will
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determine the size of the array needed to store the argument
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attributes. */
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@ -1721,11 +1727,39 @@ do_positional:
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if (nspecs * sizeof (*specs) >= nspecs_size)
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{
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/* Extend the array of format specifiers. */
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if (nspecs_size * 2 < nspecs_size)
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{
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__set_errno (ENOMEM);
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done = -1;
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goto all_done;
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}
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struct printf_spec *old = specs;
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if (__libc_use_alloca (2 * nspecs_size))
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specs = extend_alloca (specs, nspecs_size, 2 * nspecs_size);
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else
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{
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nspecs_size *= 2;
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specs = malloc (nspecs_size);
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if (specs == NULL)
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{
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__set_errno (ENOMEM);
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specs = old;
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done = -1;
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goto all_done;
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}
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}
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/* Copy the old array's elements to the new space. */
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memmove (specs, old, nspecs * sizeof (*specs));
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/* If we had previously malloc'd space for SPECS, then
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release it after the copy is complete. */
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if (specs_malloced)
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free (old);
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/* Now set SPECS_MALLOCED if needed. */
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if (!__libc_use_alloca (nspecs_size))
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specs_malloced = true;
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}
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/* Parse the format specifier. */
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@ -2046,6 +2080,8 @@ do_positional:
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}
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all_done:
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if (specs_malloced)
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free (specs);
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if (__glibc_unlikely (args_malloced != NULL))
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free (args_malloced);
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if (__glibc_unlikely (workstart != NULL))
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