[PATCH] erofs-utils: dump: fix stack-overflow due to directory loops

[Gao Xiang <hsiangkao@linux.alibaba.com>]

This mirrors the solution in commit f3728a162d22 ("erofs-utils: dump:
fix stack-overflow due to directory loops").

Reported-by: Tristan <TristanInSec@gmail.com>
Fixes: 5a9ac8e057cf ("erofs-utils: dump: convert readdir to use erofs_iterate_dir()")
Closes: https://lore.kernel.org/r/CAA1XrhPMekMqAnRkC-jV9rTsO4LHjzh=kxn6zQKMgBrqfrnp8A@mail.gmail.com/6-dump-erofs-recursion.txt
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
---
 dump/main.c | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/dump/main.c b/dump/main.c
index 6c7258a5db40..9eebcb8a3e3f 100644
--- a/dump/main.c
+++ b/dump/main.c
@@ -17,7 +17,13 @@
 #include "../lib/liberofs_private.h"
 #include "../lib/liberofs_uuid.h"
 
+struct erofsdump_dirstack {
+       erofs_nid_t dirs[PATH_MAX];
+       int top;
+};
+
 struct erofsdump_cfg {
+	struct erofsdump_dirstack dirstack;
 	unsigned int totalshow;
 	bool show_inode;
 	bool show_extent;
@@ -359,7 +365,6 @@ static int erofsdump_readdir(struct erofs_dir_context *ctx)
 		update_file_size_statistics(occupied_size, false);
 	}
 
-	/* XXXX: the dir depth should be restricted in order to avoid loops */
 	if (S_ISDIR(vi.i_mode)) {
 		struct erofs_dir_context nctx = {
 			.flags = ctx->dir ? EROFS_READDIR_VALID_PNID : 0,
@@ -367,8 +372,18 @@ static int erofsdump_readdir(struct erofs_dir_context *ctx)
 			.dir = &vi,
 			.cb = erofsdump_dirent_iter,
 		};
-
-		return erofs_iterate_dir(&nctx, false);
+		int i, ret;
+
+		/* XXX: support the deeper cases later */
+		if (dumpcfg.dirstack.top >= ARRAY_SIZE(dumpcfg.dirstack.dirs))
+			return -ENAMETOOLONG;
+		for (i = 0; i < dumpcfg.dirstack.top; ++i)
+			if (vi.nid == dumpcfg.dirstack.dirs[i])
+				return -ELOOP;
+		dumpcfg.dirstack.dirs[dumpcfg.dirstack.top++] = nctx.pnid;
+		ret = erofs_iterate_dir(&nctx, false);
+		--dumpcfg.dirstack.top;
+		return ret;
 	}
 	return 0;
 }
-- 
2.43.5