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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
63 lines
1.6 KiB
C
63 lines
1.6 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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/*
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* Copyright 2006 Ricardo Correia. All rights reserved.
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* Use is subject to license terms.
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*/
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#include <unistd.h>
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#include <stdio.h>
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#include <errno.h>
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#include <stdlib.h>
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#include <limits.h>
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#include <string.h>
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#include <zone.h>
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zoneid_t
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getzoneid(void)
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{
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char path[PATH_MAX];
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char buf[128] = { '\0' };
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char *cp;
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int c = snprintf(path, sizeof (path), "/proc/self/ns/user");
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/* This API doesn't have any error checking... */
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if (c < 0 || c >= sizeof (path))
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return (0);
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ssize_t r = readlink(path, buf, sizeof (buf) - 1);
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if (r < 0)
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return (0);
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cp = strchr(buf, '[');
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if (cp == NULL)
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return (0);
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cp++;
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unsigned long n = strtoul(cp, NULL, 10);
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if (n == ULONG_MAX && errno == ERANGE)
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return (0);
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zoneid_t z = (zoneid_t)n;
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return (z);
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}
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