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`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
114 lines
3.9 KiB
C
114 lines
3.9 KiB
C
/*
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* Copyright (c) 2007 Pawel Jakub Dawidek <pjd@FreeBSD.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* $FreeBSD$
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*/
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#ifndef _OPENSOLARIS_SYS_KMEM_H_
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#define _OPENSOLARIS_SYS_KMEM_H_
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#ifdef _KERNEL
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#include <sys/param.h>
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#include <sys/malloc.h>
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#include <sys/vmem.h>
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#include <sys/counter.h>
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#include <vm/uma.h>
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#include <vm/vm.h>
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#include <vm/vm_extern.h>
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MALLOC_DECLARE(M_SOLARIS);
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#define POINTER_IS_VALID(p) (!((uintptr_t)(p) & 0x3))
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#define POINTER_INVALIDATE(pp) (*(pp) = (void *)((uintptr_t)(*(pp)) | 0x1))
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#define KM_SLEEP M_WAITOK
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#define KM_PUSHPAGE M_WAITOK
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#define KM_NOSLEEP M_NOWAIT
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#define KM_NORMALPRI 0
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#define KMC_NODEBUG UMA_ZONE_NODUMP
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typedef struct vmem vmem_t;
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extern char *kmem_asprintf(const char *, ...)
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__attribute__((format(printf, 1, 2)));
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extern char *kmem_vasprintf(const char *fmt, va_list ap)
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__attribute__((format(printf, 1, 0)));
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extern int kmem_scnprintf(char *restrict str, size_t size,
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const char *restrict fmt, ...);
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typedef struct kmem_cache {
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char kc_name[32];
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#if !defined(KMEM_DEBUG)
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uma_zone_t kc_zone;
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#else
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size_t kc_size;
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#endif
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int (*kc_constructor)(void *, void *, int);
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void (*kc_destructor)(void *, void *);
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void *kc_private;
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} kmem_cache_t;
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extern uint64_t spl_kmem_cache_inuse(kmem_cache_t *cache);
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extern uint64_t spl_kmem_cache_entry_size(kmem_cache_t *cache);
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__attribute__((alloc_size(1)))
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void *zfs_kmem_alloc(size_t size, int kmflags);
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void zfs_kmem_free(void *buf, size_t size);
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uint64_t kmem_size(void);
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kmem_cache_t *kmem_cache_create(const char *name, size_t bufsize, size_t align,
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int (*constructor)(void *, void *, int), void (*destructor)(void *, void *),
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void (*reclaim)(void *) __unused, void *private, vmem_t *vmp, int cflags);
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void kmem_cache_destroy(kmem_cache_t *cache);
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void *kmem_cache_alloc(kmem_cache_t *cache, int flags);
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void kmem_cache_free(kmem_cache_t *cache, void *buf);
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boolean_t kmem_cache_reap_active(void);
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void kmem_cache_reap_soon(kmem_cache_t *);
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void kmem_reap(void);
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int kmem_debugging(void);
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void *calloc(size_t n, size_t s);
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#define kmem_cache_reap_now kmem_cache_reap_soon
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#define freemem vm_free_count()
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#define minfree vm_cnt.v_free_min
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#define kmem_alloc(size, kmflags) zfs_kmem_alloc((size), (kmflags))
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#define kmem_zalloc(size, kmflags) \
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zfs_kmem_alloc((size), (kmflags) | M_ZERO)
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#define kmem_free(buf, size) zfs_kmem_free((buf), (size))
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#endif /* _KERNEL */
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#ifdef _STANDALONE
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/*
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* At the moment, we just need it for the type. We redirect the alloc/free
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* routines to the usual Free and Malloc in that environment.
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*/
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typedef int kmem_cache_t;
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#endif /* _STANDALONE */
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#endif /* _OPENSOLARIS_SYS_KMEM_H_ */
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