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97143b9d31
`snprintf()` is meant to protect against buffer overflows, but operating on the buffer using its return value, possibly by calling it again, can cause a buffer overflow, because it will return how many characters it would have written if it had enough space even when it did not. In a number of places, we repeatedly call snprintf() by successively incrementing a buffer offset and decrementing a buffer length, by its return value. This is a potentially unsafe usage of `snprintf()` whenever the buffer length is reached. CodeQL complained about this. To fix this, we introduce `kmem_scnprintf()`, which will return 0 when the buffer is zero or the number of written characters, minus 1 to exclude the NULL character, when the buffer was too small. In all other cases, it behaves like snprintf(). The name is inspired by the Linux and XNU kernels' `scnprintf()`. The implementation was written before I thought to look at `scnprintf()` and had a good name for it, but it turned out to have identical semantics to the Linux kernel version. That lead to the name, `kmem_scnprintf()`. CodeQL only catches this issue in loops, so repeated use of snprintf() outside of a loop was not caught. As a result, a thorough audit of the codebase was done to examine all instances of `snprintf()` usage for potential problems and a few were caught. Fixes for them are included in this patch. Unfortunately, ZED is one of the places where `snprintf()` is potentially used incorrectly. Since using `kmem_scnprintf()` in it would require changing how it is linked, we modify its usage to make it safe, no matter what buffer length is used. In addition, there was a bug in the use of the return value where the NULL format character was not being written by pwrite(). That has been fixed. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Richard Yao <richard.yao@alumni.stonybrook.edu> Closes #14098
138 lines
3.1 KiB
C
138 lines
3.1 KiB
C
/*
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* CDDL HEADER START
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*
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* The contents of this file are subject to the terms of the
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* Common Development and Distribution License (the "License").
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* You may not use this file except in compliance with the License.
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*
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* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
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* or https://opensource.org/licenses/CDDL-1.0.
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* See the License for the specific language governing permissions
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* and limitations under the License.
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*
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* When distributing Covered Code, include this CDDL HEADER in each
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* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
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* If applicable, add the following below this CDDL HEADER, with the
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* fields enclosed by brackets "[]" replaced with your own identifying
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* information: Portions Copyright [yyyy] [name of copyright owner]
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*
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* CDDL HEADER END
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*
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* $FreeBSD$
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*/
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/*
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* Copyright 2007 Sun Microsystems, Inc. All rights reserved.
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* Use is subject to license terms.
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*/
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#include <sys/types.h>
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#include <sys/param.h>
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#include <sys/string.h>
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#include <sys/kmem.h>
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#include <machine/stdarg.h>
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#define IS_DIGIT(c) ((c) >= '0' && (c) <= '9')
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#define IS_ALPHA(c) \
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(((c) >= 'a' && (c) <= 'z') || ((c) >= 'A' && (c) <= 'Z'))
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char *
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strpbrk(const char *s, const char *b)
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{
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const char *p;
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do {
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for (p = b; *p != '\0' && *p != *s; ++p)
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;
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if (*p != '\0')
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return ((char *)s);
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} while (*s++);
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return (NULL);
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}
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/*
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* Convert a string into a valid C identifier by replacing invalid
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* characters with '_'. Also makes sure the string is nul-terminated
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* and takes up at most n bytes.
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*/
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void
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strident_canon(char *s, size_t n)
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{
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char c;
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char *end = s + n - 1;
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if ((c = *s) == 0)
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return;
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if (!IS_ALPHA(c) && c != '_')
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*s = '_';
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while (s < end && ((c = *(++s)) != 0)) {
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if (!IS_ALPHA(c) && !IS_DIGIT(c) && c != '_')
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*s = '_';
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}
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*s = 0;
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}
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/*
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* Do not change the length of the returned string; it must be freed
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* with strfree().
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*/
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char *
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kmem_asprintf(const char *fmt, ...)
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{
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int size;
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va_list adx;
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char *buf;
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va_start(adx, fmt);
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size = vsnprintf(NULL, 0, fmt, adx) + 1;
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va_end(adx);
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buf = kmem_alloc(size, KM_SLEEP);
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va_start(adx, fmt);
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(void) vsnprintf(buf, size, fmt, adx);
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va_end(adx);
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return (buf);
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}
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void
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kmem_strfree(char *str)
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{
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ASSERT3P(str, !=, NULL);
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kmem_free(str, strlen(str) + 1);
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}
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/*
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* kmem_scnprintf() will return the number of characters that it would have
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* printed whenever it is limited by value of the size variable, rather than
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* the number of characters that it did print. This can cause misbehavior on
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* subsequent uses of the return value, so we define a safe version that will
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* return the number of characters actually printed, minus the NULL format
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* character. Subsequent use of this by the safe string functions is safe
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* whether it is snprintf(), strlcat() or strlcpy().
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*/
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int
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kmem_scnprintf(char *restrict str, size_t size, const char *restrict fmt, ...)
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{
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int n;
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va_list ap;
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/* Make the 0 case a no-op so that we do not return -1 */
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if (size == 0)
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return (0);
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va_start(ap, fmt);
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n = vsnprintf(str, size, fmt, ap);
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va_end(ap);
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if (n >= size)
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n = size - 1;
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return (n);
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}
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