From: Tobias Stoeckmann <tobias@stoeckmann.org>
Date: Fri, 27 Jun 2025 15:24:15 +0000 (+0200)
Subject: Do not truncate seek requests
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=3997a5f28a3988f3ec6a288dc5f9f5abb3439249;p=thirdparty%2Flibarchive.git

Do not truncate seek requests

If a seek cannot be fulfilled, fail directly with EOVERFLOW to match
regular lseek behavior.

Signed-off-by: Tobias Stoeckmann <tobias@stoeckmann.org>
---

diff --git a/libarchive/archive_read_open_fd.c b/libarchive/archive_read_open_fd.c
index edb78b032..c85a62a3e 100644
--- a/libarchive/archive_read_open_fd.c
+++ b/libarchive/archive_read_open_fd.c
@@ -193,21 +193,22 @@ file_seek(struct archive *a, void *client_data, int64_t request, int whence)
 
 	/* We use off_t here because lseek() is declared that way. */
 
-	/* Reduce a request that would overflow the 'seek' variable. */
+	/* Do not perform a seek which cannot be fulfilled. */
 	if (sizeof(request) > sizeof(seek)) {
 		const int64_t max_seek =
 		    (((int64_t)1 << (seek_bits - 1)) - 1) * 2 + 1;
 		const int64_t min_seek = ~max_seek;
-		if (request > max_seek)
-			seek = (off_t)max_seek;
-		else if (request < min_seek)
-			seek = (off_t)min_seek;
+		if (request < min_seek || request > max_seek) {
+			errno = EOVERFLOW;
+			goto err;
+		}
 	}
 
 	r = lseek(mine->fd, seek, whence);
 	if (r >= 0)
 		return r;
 
+err:
 	if (errno == ESPIPE) {
 		archive_set_error(a, errno,
 		    "A file descriptor(%d) is not seekable(PIPE)", mine->fd);
diff --git a/libarchive/archive_read_open_file.c b/libarchive/archive_read_open_file.c
index b0eb5b0ea..6ca2ff191 100644
--- a/libarchive/archive_read_open_file.c
+++ b/libarchive/archive_read_open_file.c
@@ -206,15 +206,15 @@ FILE_seek(struct archive *a, void *client_data, int64_t request, int whence)
 	int seek_bits = sizeof(seek) * 8 - 1;
 	(void)a; /* UNUSED */
 
-	/* Reduce a request that would overflow the 'seek' variable. */
+	/* Do not perform a seek which cannot be fulfilled. */
 	if (sizeof(request) > sizeof(seek)) {
 		const int64_t max_seek =
 		    (((int64_t)1 << (seek_bits - 1)) - 1) * 2 + 1;
 		const int64_t min_seek = ~max_seek;
-		if (request > max_seek)
-			seek = max_seek;
-		else if (request < min_seek)
-			seek = min_seek;
+		if (request < min_seek || request > max_seek) {
+			errno = EOVERFLOW;
+			goto err;
+		}
 	}
 
 #ifdef __ANDROID__
@@ -237,6 +237,7 @@ FILE_seek(struct archive *a, void *client_data, int64_t request, int whence)
 	}
 #endif
 	/* If we arrive here, the input is corrupted or truncated so fail. */
+err:
 	archive_set_error(a, errno, "Error seeking in FILE* pointer");
 	return (ARCHIVE_FATAL);
 }
diff --git a/libarchive/archive_read_open_filename.c b/libarchive/archive_read_open_filename.c
index b9d30bf44..a910eefcb 100644
--- a/libarchive/archive_read_open_filename.c
+++ b/libarchive/archive_read_open_filename.c
@@ -564,15 +564,15 @@ file_seek(struct archive *a, void *client_data, int64_t request, int whence)
 
 	/* We use off_t here because lseek() is declared that way. */
 
-	/* Reduce a request that would overflow the 'seek' variable. */
+	/* Do not perform a seek which cannot be fulfilled. */
 	if (sizeof(request) > sizeof(seek)) {
 		const int64_t max_seek =
 		    (((int64_t)1 << (seek_bits - 1)) - 1) * 2 + 1;
 		const int64_t min_seek = ~max_seek;
-		if (request > max_seek)
-			seek = (off_t)max_seek;
-		else if (request < min_seek)
-			seek = (off_t)min_seek;
+		if (request < min_seek || request > max_seek) {
+			errno = EOVERFLOW;
+			goto err;
+		}
 	}
 
 	r = lseek(mine->fd, seek, whence);
@@ -580,6 +580,7 @@ file_seek(struct archive *a, void *client_data, int64_t request, int whence)
 		return r;
 
 	/* If the input is corrupted or truncated, fail. */
+err:
 	if (mine->filename_type == FNT_STDIN)
 		archive_set_error(a, errno, "Error seeking in stdin");
 	else if (mine->filename_type == FNT_MBS)