From: Gao Xiang <hsiangkao@linux.alibaba.com>
Date: Fri, 28 Feb 2025 04:54:26 +0000 (+0800)
Subject: erofs-utils: tar: handle empty filenames correctly
X-Git-Tag: accepted/tizen/unified/20250610.081809~31
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=ffa517605bf978cd76a4449143b1aad8b534d901;p=platform%2Fupstream%2Ferofs-utils.git

erofs-utils: tar: handle empty filenames correctly

Tar entries with empty filenames are unusual but shouldn't
cause a crash.  Handle this by following `tar` behavior:
substitute `.` for the empty filenames.

Reproducible image (base64-encoded gzipped blob):
H4sICL2XwGcAA3Rlc3RfcmVhZF9mb3JtYXRfdGFyX2VtcHR5X2ZpbGVuYW1lLnRhcgBjY
KA9MDAwMDc3VQDShuamBiAaBGA0hGNoaGBgZGJsaAZUaADiGDIomNLBbQylxSWJRUCnlG
Tm4lVXnpGamoNHHtVTClR14ygYBaNgFNAAAAAE6urMAAYAAA==

Fixes: 95d315fd7958 ("erofs-utils: introduce tarerofs")
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20250228045426.81099-1-hsiangkao@linux.alibaba.com
---

diff --git a/lib/tar.c b/lib/tar.c
index 2ea3858..941fad2 100644
--- a/lib/tar.c
+++ b/lib/tar.c
@@ -826,8 +826,14 @@ out_eot:
 		memcpy(path + j, th->name, sizeof(th->name));
 		path[j + sizeof(th->name)] = '\0';
 		j = strlen(path);
-		while (path[j - 1] == '/')
-			path[--j] = '\0';
+		if (__erofs_unlikely(!j)) {
+			erofs_info("substituting '.' for empty filename");
+			path[0] = '.';
+			path[1] = '\0';
+		} else {
+			while (path[j - 1] == '/')
+				path[--j] = '\0';
+		}
 	}
 
 	dataoff = tar->offset;