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Subject[PATCH 4.19 127/134] staging: erofs: keep corrupted fs from crashing kernel in erofs_readdir()
Date
4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Gao Xiang <gaoxiang25@huawei.com>

commit 33bac912840fe64dbc15556302537dc6a17cac63 upstream.

After commit 419d6efc50e9, kernel cannot be crashed in the namei
path. However, corrupted nameoff can do harm in the process of
readdir for scenerios without dm-verity as well. Fix it now.

Fixes: 3aa8ec716e52 ("staging: erofs: add directory operations")
Cc: <stable@vger.kernel.org> # 4.19+
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>


---
drivers/staging/erofs/dir.c | 45 ++++++++++++++++++++++++--------------------
1 file changed, 25 insertions(+), 20 deletions(-)

--- a/drivers/staging/erofs/dir.c
+++ b/drivers/staging/erofs/dir.c
@@ -23,6 +23,21 @@ static const unsigned char erofs_filetyp
[EROFS_FT_SYMLINK] = DT_LNK,
};

+static void debug_one_dentry(unsigned char d_type, const char *de_name,
+ unsigned int de_namelen)
+{
+#ifdef CONFIG_EROFS_FS_DEBUG
+ /* since the on-disk name could not have the trailing '\0' */
+ unsigned char dbg_namebuf[EROFS_NAME_LEN + 1];
+
+ memcpy(dbg_namebuf, de_name, de_namelen);
+ dbg_namebuf[de_namelen] = '\0';
+
+ debugln("found dirent %s de_len %u d_type %d", dbg_namebuf,
+ de_namelen, d_type);
+#endif
+}
+
static int erofs_fill_dentries(struct dir_context *ctx,
void *dentry_blk, unsigned *ofs,
unsigned nameoff, unsigned maxsize)
@@ -33,14 +48,10 @@ static int erofs_fill_dentries(struct di
de = dentry_blk + *ofs;
while (de < end) {
const char *de_name;
- int de_namelen;
+ unsigned int de_namelen;
unsigned char d_type;
-#ifdef CONFIG_EROFS_FS_DEBUG
- unsigned dbg_namelen;
- unsigned char dbg_namebuf[EROFS_NAME_LEN];
-#endif

- if (unlikely(de->file_type < EROFS_FT_MAX))
+ if (de->file_type < EROFS_FT_MAX)
d_type = erofs_filetype_table[de->file_type];
else
d_type = DT_UNKNOWN;
@@ -48,26 +59,20 @@ static int erofs_fill_dentries(struct di
nameoff = le16_to_cpu(de->nameoff);
de_name = (char *)dentry_blk + nameoff;

- de_namelen = unlikely(de + 1 >= end) ?
- /* last directory entry */
- strnlen(de_name, maxsize - nameoff) :
- le16_to_cpu(de[1].nameoff) - nameoff;
+ /* the last dirent in the block? */
+ if (de + 1 >= end)
+ de_namelen = strnlen(de_name, maxsize - nameoff);
+ else
+ de_namelen = le16_to_cpu(de[1].nameoff) - nameoff;

/* a corrupted entry is found */
- if (unlikely(de_namelen < 0)) {
+ if (unlikely(nameoff + de_namelen > maxsize ||
+ de_namelen > EROFS_NAME_LEN)) {
DBG_BUGON(1);
return -EIO;
}

-#ifdef CONFIG_EROFS_FS_DEBUG
- dbg_namelen = min(EROFS_NAME_LEN - 1, de_namelen);
- memcpy(dbg_namebuf, de_name, dbg_namelen);
- dbg_namebuf[dbg_namelen] = '\0';
-
- debugln("%s, found de_name %s de_len %d d_type %d", __func__,
- dbg_namebuf, de_namelen, d_type);
-#endif
-
+ debug_one_dentry(d_type, de_name, de_namelen);
if (!dir_emit(ctx, de_name, de_namelen,
le64_to_cpu(de->nid), d_type))
/* stoped by some reason */

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