From 12495ea3ac47ec5b53611e0d68ba3222a09784d1 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Krzysztof=20B=C5=82aszkowski?= Date: Sun, 12 Jun 2016 19:26:45 +0200 Subject: [PATCH] freevxfs: refactor readdir and lookup code MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This change fixes also a buffer overflow which was caused by accessing address space beyond mapped page Signed-off-by: Krzysztof Błaszkowski Signed-off-by: Christoph Hellwig --- fs/freevxfs/vxfs_lookup.c | 223 ++++++++++++++++++-------------------- 1 file changed, 103 insertions(+), 120 deletions(-) diff --git a/fs/freevxfs/vxfs_lookup.c b/fs/freevxfs/vxfs_lookup.c index f042cafbb85f..ce4785fd81c6 100644 --- a/fs/freevxfs/vxfs_lookup.c +++ b/fs/freevxfs/vxfs_lookup.c @@ -62,35 +62,6 @@ const struct file_operations vxfs_dir_operations = { .iterate_shared = vxfs_readdir, }; -static inline u_long -dir_blocks(struct inode *ip) -{ - u_long bsize = ip->i_sb->s_blocksize; - return (ip->i_size + bsize - 1) & ~(bsize - 1); -} - -/* - * NOTE! unlike strncmp, vxfs_match returns 1 for success, 0 for failure. - * - * len <= VXFS_NAMELEN and de != NULL are guaranteed by caller. - */ -static inline int -vxfs_match(struct vxfs_sb_info *sbi, int len, const char *const name, - struct vxfs_direct *de) -{ - if (len != fs16_to_cpu(sbi, de->d_namelen)) - return 0; - if (!de->d_ino) - return 0; - return !memcmp(name, de->d_name, len); -} - -static inline struct vxfs_direct * -vxfs_next_entry(struct vxfs_sb_info *sbi, struct vxfs_direct *de) -{ - return ((struct vxfs_direct *) - ((char *)de + fs16_to_cpu(sbi, de->d_reclen))); -} /** * vxfs_find_entry - find a mathing directory entry for a dentry @@ -109,53 +80,64 @@ vxfs_next_entry(struct vxfs_sb_info *sbi, struct vxfs_direct *de) static struct vxfs_direct * vxfs_find_entry(struct inode *ip, struct dentry *dp, struct page **ppp) { - struct vxfs_sb_info *sbi = VXFS_SBI(ip->i_sb); - u_long npages, page, nblocks, pblocks, block; - u_long bsize = ip->i_sb->s_blocksize; - const char *name = dp->d_name.name; - int namelen = dp->d_name.len; + u_long bsize = ip->i_sb->s_blocksize; + const char *name = dp->d_name.name; + int namelen = dp->d_name.len; + loff_t limit = VXFS_DIRROUND(ip->i_size); + struct vxfs_direct *de_exit = NULL; + loff_t pos = 0; + struct vxfs_sb_info *sbi = VXFS_SBI(ip->i_sb); - npages = dir_pages(ip); - nblocks = dir_blocks(ip); - pblocks = VXFS_BLOCK_PER_PAGE(ip->i_sb); - - for (page = 0; page < npages; page++) { - caddr_t kaddr; - struct page *pp; + while (pos < limit) { + struct page *pp; + char *kaddr; + int pg_ofs = pos & ~PAGE_MASK; - pp = vxfs_get_page(ip->i_mapping, page); + pp = vxfs_get_page(ip->i_mapping, pos >> PAGE_SHIFT); if (IS_ERR(pp)) - continue; - kaddr = (caddr_t)page_address(pp); + return NULL; + kaddr = (char *)page_address(pp); - for (block = 0; block <= nblocks && block <= pblocks; block++) { - caddr_t baddr, limit; - struct vxfs_dirblk *dbp; - struct vxfs_direct *de; + while (pg_ofs < PAGE_SIZE && pos < limit) { + struct vxfs_direct *de; - baddr = kaddr + (block * bsize); - limit = baddr + bsize - VXFS_DIRLEN(1); - - dbp = (struct vxfs_dirblk *)baddr; - de = (struct vxfs_direct *) - (baddr + VXFS_DIRBLKOV(sbi, dbp)); + if ((pos & (bsize - 1)) < 4) { + struct vxfs_dirblk *dbp = + (struct vxfs_dirblk *) + (kaddr + (pos & ~PAGE_MASK)); + int overhead = VXFS_DIRBLKOV(sbi, dbp); - for (; (caddr_t)de <= limit; - de = vxfs_next_entry(sbi, de)) { - if (!de->d_reclen) - break; - if (!de->d_ino) - continue; - if (vxfs_match(sbi, namelen, name, de)) { - *ppp = pp; - return (de); - } + pos += overhead; + pg_ofs += overhead; + } + de = (struct vxfs_direct *)(kaddr + pg_ofs); + + if (!de->d_reclen) { + pos += bsize - 1; + pos &= ~(bsize - 1); + break; + } + + pg_ofs += fs16_to_cpu(sbi, de->d_reclen); + pos += fs16_to_cpu(sbi, de->d_reclen); + if (!de->d_ino) + continue; + + if (namelen != fs16_to_cpu(sbi, de->d_namelen)) + continue; + if (!memcmp(name, de->d_name, namelen)) { + *ppp = pp; + de_exit = de; + break; } } - vxfs_put_page(pp); + if (!de_exit) + vxfs_put_page(pp); + else + break; } - return NULL; + return de_exit; } /** @@ -238,80 +220,81 @@ vxfs_readdir(struct file *fp, struct dir_context *ctx) { struct inode *ip = file_inode(fp); struct super_block *sbp = ip->i_sb; - struct vxfs_sb_info *sbi = VXFS_SBI(sbp); u_long bsize = sbp->s_blocksize; - u_long page, npages, block, pblocks, nblocks, offset; - loff_t pos; - + loff_t pos, limit; + struct vxfs_sb_info *sbi = VXFS_SBI(sbp); if (ctx->pos == 0) { if (!dir_emit_dot(fp, ctx)) - return 0; - ctx->pos = 1; + goto out; + ctx->pos++; } if (ctx->pos == 1) { if (!dir_emit(ctx, "..", 2, VXFS_INO(ip)->vii_dotdot, DT_DIR)) - return 0; - ctx->pos = 2; + goto out; + ctx->pos++; } - pos = ctx->pos - 2; - - if (pos > VXFS_DIRROUND(ip->i_size)) - return 0; - npages = dir_pages(ip); - nblocks = dir_blocks(ip); - pblocks = VXFS_BLOCK_PER_PAGE(sbp); + limit = VXFS_DIRROUND(ip->i_size); + if (ctx->pos > limit) + goto out; - page = pos >> PAGE_SHIFT; - offset = pos & ~PAGE_MASK; - block = (u_long)(pos >> sbp->s_blocksize_bits) % pblocks; + pos = ctx->pos & ~3L; - for (; page < npages; page++, block = 0) { - char *kaddr; - struct page *pp; + while (pos < limit) { + struct page *pp; + char *kaddr; + int pg_ofs = pos & ~PAGE_MASK; + int rc = 0; - pp = vxfs_get_page(ip->i_mapping, page); + pp = vxfs_get_page(ip->i_mapping, pos >> PAGE_SHIFT); if (IS_ERR(pp)) - continue; + return -ENOMEM; + kaddr = (char *)page_address(pp); - for (; block <= nblocks && block <= pblocks; block++) { - char *baddr, *limit; - struct vxfs_dirblk *dbp; - struct vxfs_direct *de; + while (pg_ofs < PAGE_SIZE && pos < limit) { + struct vxfs_direct *de; - baddr = kaddr + (block * bsize); - limit = baddr + bsize - VXFS_DIRLEN(1); - - dbp = (struct vxfs_dirblk *)baddr; - de = (struct vxfs_direct *) - (offset ? - (kaddr + offset) : - (baddr + VXFS_DIRBLKOV(sbi, dbp))); + if ((pos & (bsize - 1)) < 4) { + struct vxfs_dirblk *dbp = + (struct vxfs_dirblk *) + (kaddr + (pos & ~PAGE_MASK)); + int overhead = VXFS_DIRBLKOV(sbi, dbp); - for (; (char *)de <= limit; - de = vxfs_next_entry(sbi, de)) { - if (!de->d_reclen) - break; - if (!de->d_ino) - continue; - - offset = (char *)de - kaddr; - ctx->pos = ((page << PAGE_SHIFT) | offset) + 2; - if (!dir_emit(ctx, de->d_name, - fs16_to_cpu(sbi, de->d_namelen), - fs32_to_cpu(sbi, de->d_ino), - DT_UNKNOWN)) { - vxfs_put_page(pp); - return 0; - } + pos += overhead; + pg_ofs += overhead; + } + de = (struct vxfs_direct *)(kaddr + pg_ofs); + + if (!de->d_reclen) { + pos += bsize - 1; + pos &= ~(bsize - 1); + break; + } + + pg_ofs += fs16_to_cpu(sbi, de->d_reclen); + pos += fs16_to_cpu(sbi, de->d_reclen); + if (!de->d_ino) + continue; + + rc = dir_emit(ctx, de->d_name, + fs16_to_cpu(sbi, de->d_namelen), + fs32_to_cpu(sbi, de->d_ino), + DT_UNKNOWN); + if (!rc) { + /* the dir entry was not read, fix pos. */ + pos -= fs16_to_cpu(sbi, de->d_reclen); + break; } - offset = 0; } vxfs_put_page(pp); - offset = 0; + if (!rc) + break; } - ctx->pos = ((page << PAGE_SHIFT) | offset) + 2; + + ctx->pos = pos | 2; + +out: return 0; }