cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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dir.c (3300B)

      1// SPDX-License-Identifier: GPL-2.0-only
      2/*
      3 * Copyright (C) 2017-2018 HUAWEI, Inc.
      4 *             https://www.huawei.com/
      5 * Copyright (C) 2022, Alibaba Cloud
      6 */
      7#include "internal.h"
      8
      9static void debug_one_dentry(unsigned char d_type, const char *de_name,
     10			     unsigned int de_namelen)
     11{
     12#ifdef CONFIG_EROFS_FS_DEBUG
     13	/* since the on-disk name could not have the trailing '\0' */
     14	unsigned char dbg_namebuf[EROFS_NAME_LEN + 1];
     15
     16	memcpy(dbg_namebuf, de_name, de_namelen);
     17	dbg_namebuf[de_namelen] = '\0';
     18
     19	erofs_dbg("found dirent %s de_len %u d_type %d", dbg_namebuf,
     20		  de_namelen, d_type);
     21#endif
     22}
     23
     24static int erofs_fill_dentries(struct inode *dir, struct dir_context *ctx,
     25			       void *dentry_blk, unsigned int *ofs,
     26			       unsigned int nameoff, unsigned int maxsize)
     27{
     28	struct erofs_dirent *de = dentry_blk + *ofs;
     29	const struct erofs_dirent *end = dentry_blk + nameoff;
     30
     31	while (de < end) {
     32		const char *de_name;
     33		unsigned int de_namelen;
     34		unsigned char d_type;
     35
     36		d_type = fs_ftype_to_dtype(de->file_type);
     37
     38		nameoff = le16_to_cpu(de->nameoff);
     39		de_name = (char *)dentry_blk + nameoff;
     40
     41		/* the last dirent in the block? */
     42		if (de + 1 >= end)
     43			de_namelen = strnlen(de_name, maxsize - nameoff);
     44		else
     45			de_namelen = le16_to_cpu(de[1].nameoff) - nameoff;
     46
     47		/* a corrupted entry is found */
     48		if (nameoff + de_namelen > maxsize ||
     49		    de_namelen > EROFS_NAME_LEN) {
     50			erofs_err(dir->i_sb, "bogus dirent @ nid %llu",
     51				  EROFS_I(dir)->nid);
     52			DBG_BUGON(1);
     53			return -EFSCORRUPTED;
     54		}
     55
     56		debug_one_dentry(d_type, de_name, de_namelen);
     57		if (!dir_emit(ctx, de_name, de_namelen,
     58			      le64_to_cpu(de->nid), d_type))
     59			/* stopped by some reason */
     60			return 1;
     61		++de;
     62		*ofs += sizeof(struct erofs_dirent);
     63	}
     64	*ofs = maxsize;
     65	return 0;
     66}
     67
     68static int erofs_readdir(struct file *f, struct dir_context *ctx)
     69{
     70	struct inode *dir = file_inode(f);
     71	struct erofs_buf buf = __EROFS_BUF_INITIALIZER;
     72	const size_t dirsize = i_size_read(dir);
     73	unsigned int i = ctx->pos / EROFS_BLKSIZ;
     74	unsigned int ofs = ctx->pos % EROFS_BLKSIZ;
     75	int err = 0;
     76	bool initial = true;
     77
     78	while (ctx->pos < dirsize) {
     79		struct erofs_dirent *de;
     80		unsigned int nameoff, maxsize;
     81
     82		de = erofs_bread(&buf, dir, i, EROFS_KMAP);
     83		if (IS_ERR(de)) {
     84			erofs_err(dir->i_sb,
     85				  "fail to readdir of logical block %u of nid %llu",
     86				  i, EROFS_I(dir)->nid);
     87			err = PTR_ERR(de);
     88			break;
     89		}
     90
     91		nameoff = le16_to_cpu(de->nameoff);
     92		if (nameoff < sizeof(struct erofs_dirent) ||
     93		    nameoff >= PAGE_SIZE) {
     94			erofs_err(dir->i_sb,
     95				  "invalid de[0].nameoff %u @ nid %llu",
     96				  nameoff, EROFS_I(dir)->nid);
     97			err = -EFSCORRUPTED;
     98			goto skip_this;
     99		}
    100
    101		maxsize = min_t(unsigned int,
    102				dirsize - ctx->pos + ofs, PAGE_SIZE);
    103
    104		/* search dirents at the arbitrary position */
    105		if (initial) {
    106			initial = false;
    107
    108			ofs = roundup(ofs, sizeof(struct erofs_dirent));
    109			if (ofs >= nameoff)
    110				goto skip_this;
    111		}
    112
    113		err = erofs_fill_dentries(dir, ctx, de, &ofs,
    114					  nameoff, maxsize);
    115skip_this:
    116		ctx->pos = blknr_to_addr(i) + ofs;
    117
    118		if (err)
    119			break;
    120		++i;
    121		ofs = 0;
    122	}
    123	erofs_put_metabuf(&buf);
    124	return err < 0 ? err : 0;
    125}
    126
    127const struct file_operations erofs_dir_fops = {
    128	.llseek		= generic_file_llseek,
    129	.read		= generic_read_dir,
    130	.iterate_shared	= erofs_readdir,
    131};