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![Bernd Schmidt](/assets/img/avatar_default.png)
An interestingly corrupted romfs file system exposed a problem with the romfs_dev_strnlen function: it's passing the wrong value to its helpers. Rather than limit the string to the length passed in by the callers, it uses the size of the device as the limit. Signed-off-by: Bernd Schmidt <bernds_cb1@t-online.de> Signed-off-by: Mike Frysinger <vapier@gentoo.org> Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
293 lines
6.4 KiB
C
293 lines
6.4 KiB
C
/* RomFS storage access routines
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*
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* Copyright © 2007 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <linux/fs.h>
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#include <linux/mtd/super.h>
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#include <linux/buffer_head.h>
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#include "internal.h"
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#if !defined(CONFIG_ROMFS_ON_MTD) && !defined(CONFIG_ROMFS_ON_BLOCK)
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#error no ROMFS backing store interface configured
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#endif
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#ifdef CONFIG_ROMFS_ON_MTD
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#define ROMFS_MTD_READ(sb, ...) ((sb)->s_mtd->read((sb)->s_mtd, ##__VA_ARGS__))
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/*
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* read data from an romfs image on an MTD device
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*/
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static int romfs_mtd_read(struct super_block *sb, unsigned long pos,
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void *buf, size_t buflen)
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{
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size_t rlen;
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int ret;
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ret = ROMFS_MTD_READ(sb, pos, buflen, &rlen, buf);
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return (ret < 0 || rlen != buflen) ? -EIO : 0;
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}
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/*
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* determine the length of a string in a romfs image on an MTD device
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*/
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static ssize_t romfs_mtd_strnlen(struct super_block *sb,
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unsigned long pos, size_t maxlen)
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{
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ssize_t n = 0;
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size_t segment;
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u_char buf[16], *p;
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size_t len;
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int ret;
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/* scan the string up to 16 bytes at a time */
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while (maxlen > 0) {
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segment = min_t(size_t, maxlen, 16);
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ret = ROMFS_MTD_READ(sb, pos, segment, &len, buf);
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if (ret < 0)
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return ret;
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p = memchr(buf, 0, len);
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if (p)
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return n + (p - buf);
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maxlen -= len;
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pos += len;
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n += len;
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}
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return n;
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}
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/*
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* compare a string to one in a romfs image on MTD
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* - return 1 if matched, 0 if differ, -ve if error
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*/
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static int romfs_mtd_strcmp(struct super_block *sb, unsigned long pos,
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const char *str, size_t size)
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{
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u_char buf[17];
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size_t len, segment;
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int ret;
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/* scan the string up to 16 bytes at a time, and attempt to grab the
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* trailing NUL whilst we're at it */
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buf[0] = 0xff;
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while (size > 0) {
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segment = min_t(size_t, size + 1, 17);
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ret = ROMFS_MTD_READ(sb, pos, segment, &len, buf);
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if (ret < 0)
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return ret;
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len--;
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if (memcmp(buf, str, len) != 0)
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return 0;
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buf[0] = buf[len];
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size -= len;
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pos += len;
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str += len;
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}
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/* check the trailing NUL was */
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if (buf[0])
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return 0;
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return 1;
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}
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#endif /* CONFIG_ROMFS_ON_MTD */
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#ifdef CONFIG_ROMFS_ON_BLOCK
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/*
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* read data from an romfs image on a block device
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*/
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static int romfs_blk_read(struct super_block *sb, unsigned long pos,
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void *buf, size_t buflen)
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{
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struct buffer_head *bh;
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unsigned long offset;
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size_t segment;
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/* copy the string up to blocksize bytes at a time */
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while (buflen > 0) {
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offset = pos & (ROMBSIZE - 1);
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segment = min_t(size_t, buflen, ROMBSIZE - offset);
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bh = sb_bread(sb, pos >> ROMBSBITS);
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if (!bh)
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return -EIO;
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memcpy(buf, bh->b_data + offset, segment);
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brelse(bh);
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buf += segment;
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buflen -= segment;
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pos += segment;
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}
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return 0;
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}
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/*
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* determine the length of a string in romfs on a block device
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*/
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static ssize_t romfs_blk_strnlen(struct super_block *sb,
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unsigned long pos, size_t limit)
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{
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struct buffer_head *bh;
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unsigned long offset;
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ssize_t n = 0;
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size_t segment;
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u_char *buf, *p;
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/* scan the string up to blocksize bytes at a time */
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while (limit > 0) {
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offset = pos & (ROMBSIZE - 1);
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segment = min_t(size_t, limit, ROMBSIZE - offset);
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bh = sb_bread(sb, pos >> ROMBSBITS);
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if (!bh)
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return -EIO;
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buf = bh->b_data + offset;
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p = memchr(buf, 0, segment);
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brelse(bh);
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if (p)
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return n + (p - buf);
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limit -= segment;
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pos += segment;
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n += segment;
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}
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return n;
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}
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/*
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* compare a string to one in a romfs image on a block device
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* - return 1 if matched, 0 if differ, -ve if error
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*/
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static int romfs_blk_strcmp(struct super_block *sb, unsigned long pos,
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const char *str, size_t size)
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{
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struct buffer_head *bh;
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unsigned long offset;
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size_t segment;
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bool matched, terminated = false;
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/* compare string up to a block at a time */
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while (size > 0) {
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offset = pos & (ROMBSIZE - 1);
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segment = min_t(size_t, size, ROMBSIZE - offset);
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bh = sb_bread(sb, pos >> ROMBSBITS);
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if (!bh)
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return -EIO;
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matched = (memcmp(bh->b_data + offset, str, segment) == 0);
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size -= segment;
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pos += segment;
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str += segment;
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if (matched && size == 0 && offset + segment < ROMBSIZE) {
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if (!bh->b_data[offset + segment])
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terminated = true;
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else
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matched = false;
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}
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brelse(bh);
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if (!matched)
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return 0;
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}
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if (!terminated) {
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/* the terminating NUL must be on the first byte of the next
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* block */
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BUG_ON((pos & (ROMBSIZE - 1)) != 0);
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bh = sb_bread(sb, pos >> ROMBSBITS);
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if (!bh)
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return -EIO;
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matched = !bh->b_data[0];
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brelse(bh);
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if (!matched)
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return 0;
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}
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return 1;
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}
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#endif /* CONFIG_ROMFS_ON_BLOCK */
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/*
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* read data from the romfs image
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*/
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int romfs_dev_read(struct super_block *sb, unsigned long pos,
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void *buf, size_t buflen)
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{
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size_t limit;
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limit = romfs_maxsize(sb);
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if (pos >= limit)
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return -EIO;
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if (buflen > limit - pos)
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buflen = limit - pos;
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#ifdef CONFIG_ROMFS_ON_MTD
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if (sb->s_mtd)
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return romfs_mtd_read(sb, pos, buf, buflen);
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#endif
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#ifdef CONFIG_ROMFS_ON_BLOCK
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if (sb->s_bdev)
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return romfs_blk_read(sb, pos, buf, buflen);
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#endif
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return -EIO;
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}
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/*
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* determine the length of a string in romfs
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*/
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ssize_t romfs_dev_strnlen(struct super_block *sb,
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unsigned long pos, size_t maxlen)
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{
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size_t limit;
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limit = romfs_maxsize(sb);
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if (pos >= limit)
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return -EIO;
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if (maxlen > limit - pos)
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maxlen = limit - pos;
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#ifdef CONFIG_ROMFS_ON_MTD
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if (sb->s_mtd)
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return romfs_mtd_strnlen(sb, pos, maxlen);
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#endif
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#ifdef CONFIG_ROMFS_ON_BLOCK
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if (sb->s_bdev)
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return romfs_blk_strnlen(sb, pos, maxlen);
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#endif
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return -EIO;
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}
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/*
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* compare a string to one in romfs
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* - the string to be compared to, str, may not be NUL-terminated; instead the
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* string is of the specified size
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* - return 1 if matched, 0 if differ, -ve if error
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*/
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int romfs_dev_strcmp(struct super_block *sb, unsigned long pos,
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const char *str, size_t size)
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{
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size_t limit;
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limit = romfs_maxsize(sb);
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if (pos >= limit)
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return -EIO;
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if (size > ROMFS_MAXFN)
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return -ENAMETOOLONG;
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if (size + 1 > limit - pos)
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return -EIO;
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#ifdef CONFIG_ROMFS_ON_MTD
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if (sb->s_mtd)
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return romfs_mtd_strcmp(sb, pos, str, size);
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#endif
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#ifdef CONFIG_ROMFS_ON_BLOCK
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if (sb->s_bdev)
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return romfs_blk_strcmp(sb, pos, str, size);
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#endif
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return -EIO;
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}
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