[PATCH v3 1/2] erofs-utils: lib/tar: skip PAX entries with empty path

[Utkal Singh <singhutkal015@gmail.com>]

When a PAX extended header contains 'path=' with an empty value,
the computed length becomes zero. The subsequent trailing-slash
removal loop accesses eh->path[j - 1] where j is zero, resulting
in an out-of-bounds read and undefined behavior.

Skip such entries to avoid unsafe pointer arithmetic and invalid
filename handling.

Signed-off-by: Utkal Singh <singhutkal015@gmail.com>
---
 lib/tar.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/lib/tar.c b/lib/tar.c
index 26461f8..be86984 100644
--- a/lib/tar.c
+++ b/lib/tar.c
@@ -510,6 +510,8 @@ int tarerofs_parse_pax_header(struct erofs_iostream *ios,
 
 			if (!strncmp(kv, "path=", sizeof("path=") - 1)) {
 				int j = p - 1 - value;
+				if (!j)
+					continue;
 				free(eh->path);
 				eh->path = strdup(value);
 				while (eh->path[j - 1] == '/')
-- 
2.43.0