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Revision 7ff57e98fb78ad94edafbdc7435f2d745e9e6bb5 authored by Fabio M. De Francesco on 23 February 2022, 10:02:52 UTC, committed by Jakub Kicinski on 24 February 2022, 17:09:33 UTC 
net/smc: Use a mutex for locking "struct smc_pnettable"
 
smc_pnetid_by_table_ib() uses read_lock() and then it calls smc_pnet_apply_ib()
which, in turn, calls mutex_lock(&smc_ib_devices.mutex).

read_lock() disables preemption. Therefore, the code acquires a mutex while in
atomic context and it leads to a SAC bug.

Fix this bug by replacing the rwlock with a mutex.

Reported-and-tested-by: syzbot+4f322a6d84e991c38775@syzkaller.appspotmail.com
Fixes: 64e28b52c7a6 ("net/smc: add pnet table namespace support")
Confirmed-by: Tony Lu <tonylu@linux.alibaba.com>
Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Acked-by: Karsten Graul <kgraul@linux.ibm.com>
Link: https://lore.kernel.org/r/20220223100252.22562-1-fmdefrancesco@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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Raw File
kasprintf.c 
// SPDX-License-Identifier: GPL-2.0
/*
 *  linux/lib/kasprintf.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 */

#include <linux/stdarg.h>
#include <linux/export.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/string.h>

/* Simplified asprintf. */
char *kvasprintf(gfp_t gfp, const char *fmt, va_list ap)
{
	unsigned int first, second;
	char *p;
	va_list aq;

	va_copy(aq, ap);
	first = vsnprintf(NULL, 0, fmt, aq);
	va_end(aq);

	p = kmalloc_track_caller(first+1, gfp);
	if (!p)
		return NULL;

	second = vsnprintf(p, first+1, fmt, ap);
	WARN(first != second, "different return values (%u and %u) from vsnprintf(\"%s\", ...)",
	     first, second, fmt);

	return p;
}
EXPORT_SYMBOL(kvasprintf);

/*
 * If fmt contains no % (or is exactly %s), use kstrdup_const. If fmt
 * (or the sole vararg) points to rodata, we will then save a memory
 * allocation and string copy. In any case, the return value should be
 * freed using kfree_const().
 */
const char *kvasprintf_const(gfp_t gfp, const char *fmt, va_list ap)
{
	if (!strchr(fmt, '%'))
		return kstrdup_const(fmt, gfp);
	if (!strcmp(fmt, "%s"))
		return kstrdup_const(va_arg(ap, const char*), gfp);
	return kvasprintf(gfp, fmt, ap);
}
EXPORT_SYMBOL(kvasprintf_const);

char *kasprintf(gfp_t gfp, const char *fmt, ...)
{
	va_list ap;
	char *p;

	va_start(ap, fmt);
	p = kvasprintf(gfp, fmt, ap);
	va_end(ap);

	return p;
}
EXPORT_SYMBOL(kasprintf);
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