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erofs: fix the out-of-bounds nameoff handling for trailing dirents

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Currently we already have boundary-checks for nameoffs, but the trailing
dirents are special since the namelens are calculated with strnlen()
with unchecked nameoffs.

If a crafted EROFS has a trailing dirent with nameoff >= maxsize,
maxsize - nameoff can underflow, causing strnlen() to read past the
directory block.

nameoff0 should also be verified to be a multiple of
`sizeof(struct erofs_dirent)` as well [1].

[1] https://sashiko.dev/#/patchset/20260416063511.3173774-1-hsiangkao%40linux.alibaba.com

Fixes: 3aa8ec716e ("staging: erofs: add directory operations")
Fixes: 33bac91284 ("staging: erofs: keep corrupted fs from crashing kernel in erofs_readdir()")
Reported-by: Yuhao Jiang <danisjiang@gmail.com>
Reported-by: Junrui Luo <moonafterrain@outlook.com>
Closes: https://lore.kernel.org/r/A0FD7E0F-7558-49B0-8BC8-EB1ECDB2479A@outlook.com
Cc: stable@vger.kernel.org
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Reviewed-by: Chao Yu <chao@kernel.org>
This commit is contained in:
Gao Xiang
2026-04-21 16:56:04 +08:00
parent a5242d37c8
commit d18a3b5d33
1 changed files with 15 additions and 13 deletions
Download Patch File Download Diff File Expand all files Collapse all files
fs/erofs/dir.c
+15 -13
View File
@@ -19,20 +19,18 @@ static int erofs_fill_dentries(struct inode *dir, struct dir_context *ctx,
const char *de_name = (char *)dentry_blk + nameoff;
unsigned int de_namelen;
/* the last dirent in the block? */
if (de + 1 >= end)
de_namelen = strnlen(de_name, maxsize - nameoff);
else
/* non-trailing dirent in the directory block? */
if (de + 1 < end)
de_namelen = le16_to_cpu(de[1].nameoff) - nameoff;
else if (maxsize <= nameoff)
goto err_bogus;
else
de_namelen = strnlen(de_name, maxsize - nameoff);
/* a corrupted entry is found */
if (nameoff + de_namelen > maxsize ||
de_namelen > EROFS_NAME_LEN) {
erofs_err(dir->i_sb, "bogus dirent @ nid %llu",
EROFS_I(dir)->nid);
DBG_BUGON(1);
return -EFSCORRUPTED;
}
/* a corrupted entry is found (including negative namelen) */
if (!in_range32(de_namelen, 1, EROFS_NAME_LEN) ||
nameoff + de_namelen > maxsize)
goto err_bogus;
if (!dir_emit(ctx, de_name, de_namelen,
erofs_nid_to_ino64(EROFS_SB(dir->i_sb),
@@ -42,6 +40,10 @@ static int erofs_fill_dentries(struct inode *dir, struct dir_context *ctx,
ctx->pos += sizeof(struct erofs_dirent);
}
return 0;
err_bogus:
erofs_err(dir->i_sb, "bogus dirent @ nid %llu", EROFS_I(dir)->nid);
DBG_BUGON(1);
return -EFSCORRUPTED;
}
static int erofs_readdir(struct file *f, struct dir_context *ctx)
@@ -88,7 +90,7 @@ static int erofs_readdir(struct file *f, struct dir_context *ctx)
}
nameoff = le16_to_cpu(de->nameoff);
if (nameoff < sizeof(struct erofs_dirent) || nameoff >= bsz) {
if (!nameoff || nameoff >= bsz || (nameoff % sizeof(*de))) {
erofs_err(sb, "invalid de[0].nameoff %u @ nid %llu",
nameoff, EROFS_I(dir)->nid);
err = -EFSCORRUPTED;