[PATCH v2 2/2] erofs-utils: lib/tar: reject negative size= value in PAX header

[Utkal Singh <singhutkal015@gmail.com>]

The PAX extended header size= field is parsed into a signed long
long but no check is made for negative values before assigning to
eh->st.st_size. A crafted PAX header with size=-1 passes the
existing format check, resulting in a negative file size that can
cause incorrect memory allocation and heap corruption in subsequent
read or seek operations.

Add an explicit check to reject negative size= values with -EINVAL.

Signed-off-by: Utkal Singh <singhutkal015@gmail.com>
---
 lib/tar.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/lib/tar.c b/lib/tar.c
index be86984..6fa2cda 100644
--- a/lib/tar.c
+++ b/lib/tar.c
@@ -546,6 +546,11 @@ int tarerofs_parse_pax_header(struct erofs_iostream *ios,
 					ret = -EIO;
 					goto out;
 				}
+				if (lln < 0) {
+					erofs_err("invalid negative size= in PAX header");
+					ret = -EINVAL;
+					goto out;
+				}
 				eh->st.st_size = lln;
 				eh->use_size = true;
 			} else if (!strncmp(kv, "uid=", sizeof("uid=") - 1)) {
-- 
2.43.0