From 89b8c35ff4b5addc08a85bf5df02b407f8af1f6c Mon Sep 17 00:00:00 2001
From: Tobias Stoeckmann <stoeckmann@users.noreply.github.com>
Date: Sun, 6 Apr 2025 22:34:37 +0200
Subject: [PATCH] Improve lseek handling (#2564)

The skip functions are limited to 1 GB for cases in which libarchive
runs on a system with an off_t or long with 32 bits. This has negative
impact on 64 bit systems.

Instead, make sure that _all_ subsequent functions truncate properly.
Some of them already did and some had regressions for over 10 years.

Tests pass on Debian 12 i686 configured with --disable-largefile, i.e.
running with an off_t with 32 bits.

Casts added where needed to still pass MSVC builds.

---------

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

Upstream-Status: Backport [https://github.com/libarchive/libarchive/commit/89b8c35ff4b5addc08a85bf5df02b407f8af1f6c]
Signed-off-by: Peter Marko <peter.marko@siemens.com>
---
 libarchive/archive_read.c               |  6 ----
 libarchive/archive_read_disk_posix.c    |  3 +-
 libarchive/archive_read_open_fd.c       | 29 +++++++++++++------
 libarchive/archive_read_open_file.c     | 35 ++++++++++++-----------
 libarchive/archive_read_open_filename.c | 37 ++++++++++++++++++-------
 libarchive/test/read_open_memory.c      |  2 +-
 libarchive/test/test_sparse_basic.c     |  6 ++--
 libarchive/test/test_tar_large.c        |  2 +-
 8 files changed, 75 insertions(+), 45 deletions(-)

diff --git a/libarchive/archive_read.c b/libarchive/archive_read.c
index 822c534b..50db8701 100644
--- a/libarchive/archive_read.c
+++ b/libarchive/archive_read.c
@@ -177,15 +177,9 @@ client_skip_proxy(struct archive_read_filter *self, int64_t request)
 		return 0;
 
 	if (self->archive->client.skipper != NULL) {
-		/* Seek requests over 1GiB are broken down into
-		 * multiple seeks.  This avoids overflows when the
-		 * requests get passed through 32-bit arguments. */
-		int64_t skip_limit = (int64_t)1 << 30;
 		int64_t total = 0;
 		for (;;) {
 			int64_t get, ask = request;
-			if (ask > skip_limit)
-				ask = skip_limit;
 			get = (self->archive->client.skipper)
 				(&self->archive->archive, self->data, ask);
 			total += get;
diff --git a/libarchive/archive_read_disk_posix.c b/libarchive/archive_read_disk_posix.c
index 09965eb9..4839d62b 100644
--- a/libarchive/archive_read_disk_posix.c
+++ b/libarchive/archive_read_disk_posix.c
@@ -779,7 +779,8 @@ _archive_read_data_block(struct archive *_a, const void **buff,
 	 */
 	if (t->current_sparse->offset > t->entry_total) {
 		if (lseek(t->entry_fd,
-		    (off_t)t->current_sparse->offset, SEEK_SET) < 0) {
+		    (off_t)t->current_sparse->offset, SEEK_SET) !=
+		    t->current_sparse->offset) {
 			archive_set_error(&a->archive, errno, "Seek error");
 			r = ARCHIVE_FATAL;
 			a->archive.state = ARCHIVE_STATE_FATAL;
diff --git a/libarchive/archive_read_open_fd.c b/libarchive/archive_read_open_fd.c
index debfde20..3fd536d5 100644
--- a/libarchive/archive_read_open_fd.c
+++ b/libarchive/archive_read_open_fd.c
@@ -132,7 +132,7 @@ static int64_t
 file_skip(struct archive *a, void *client_data, int64_t request)
 {
 	struct read_fd_data *mine = (struct read_fd_data *)client_data;
-	int64_t skip = request;
+	off_t skip = (off_t)request;
 	int64_t old_offset, new_offset;
 	int skip_bits = sizeof(skip) * 8 - 1;  /* off_t is a signed type. */
 
@@ -141,15 +141,15 @@ file_skip(struct archive *a, void *client_data, int64_t request)
 
 	/* Reduce a request that would overflow the 'skip' variable. */
 	if (sizeof(request) > sizeof(skip)) {
-		int64_t max_skip =
+		const int64_t max_skip =
 		    (((int64_t)1 << (skip_bits - 1)) - 1) * 2 + 1;
 		if (request > max_skip)
-			skip = max_skip;
+			skip = (off_t)max_skip;
 	}
 
-	/* Reduce request to the next smallest multiple of block_size */
-	request = (request / mine->block_size) * mine->block_size;
-	if (request == 0)
+	/* Reduce 'skip' to the next smallest multiple of block_size */
+	skip = (off_t)(((int64_t)skip / mine->block_size) * mine->block_size);
+	if (skip == 0)
 		return (0);
 
 	if (((old_offset = lseek(mine->fd, 0, SEEK_CUR)) >= 0) &&
@@ -179,11 +179,24 @@ static int64_t
 file_seek(struct archive *a, void *client_data, int64_t request, int whence)
 {
 	struct read_fd_data *mine = (struct read_fd_data *)client_data;
+	off_t seek = (off_t)request;
 	int64_t r;
+	int seek_bits = sizeof(seek) * 8 - 1;  /* off_t is a signed type. */
 
 	/* We use off_t here because lseek() is declared that way. */
-	/* See above for notes about when off_t is less than 64 bits. */
-	r = lseek(mine->fd, request, whence);
+
+	/* Reduce a request that would overflow the 'seek' variable. */
+	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;
+	}
+
+	r = lseek(mine->fd, seek, whence);
 	if (r >= 0)
 		return r;
 
diff --git a/libarchive/archive_read_open_file.c b/libarchive/archive_read_open_file.c
index ecd56dce..2829b9a5 100644
--- a/libarchive/archive_read_open_file.c
+++ b/libarchive/archive_read_open_file.c
@@ -146,7 +146,7 @@ FILE_skip(struct archive *a, void *client_data, int64_t request)
 
 	/* If request is too big for a long or an off_t, reduce it. */
 	if (sizeof(request) > sizeof(skip)) {
-		int64_t max_skip =
+		const int64_t max_skip =
 		    (((int64_t)1 << (skip_bits - 1)) - 1) * 2 + 1;
 		if (request > max_skip)
 			skip = max_skip;
@@ -177,39 +177,42 @@ FILE_seek(struct archive *a, void *client_data, int64_t request, int whence)
 {
 	struct read_FILE_data *mine = (struct read_FILE_data *)client_data;
 #if HAVE__FSEEKI64
-	int64_t skip = request;
+	int64_t seek = request;
 #elif HAVE_FSEEKO
-	off_t skip = (off_t)request;
+	off_t seek = (off_t)request;
 #else
-	long skip = (long)request;
+	long seek = (long)request;
 #endif
-	int skip_bits = sizeof(skip) * 8 - 1;
+	int seek_bits = sizeof(seek) * 8 - 1;
 	(void)a; /* UNUSED */
 
-	/* If request is too big for a long or an off_t, reduce it. */
-	if (sizeof(request) > sizeof(skip)) {
-		int64_t max_skip =
-		    (((int64_t)1 << (skip_bits - 1)) - 1) * 2 + 1;
-		if (request > max_skip)
-			skip = max_skip;
+	/* Reduce a request that would overflow the 'seek' variable. */
+	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;
 	}
 
 #ifdef __ANDROID__
 	/* Newer Android versions have fseeko...to meditate. */
-	int64_t ret = lseek(fileno(mine->f), skip, whence);
+	int64_t ret = lseek(fileno(mine->f), seek, whence);
 	if (ret >= 0) {
 		return ret;
 	}
 #elif HAVE__FSEEKI64
-	if (_fseeki64(mine->f, skip, whence) == 0) {
+	if (_fseeki64(mine->f, seek, whence) == 0) {
 		return _ftelli64(mine->f);
 	}
 #elif HAVE_FSEEKO
-	if (fseeko(mine->f, skip, whence) == 0) {
+	if (fseeko(mine->f, seek, whence) == 0) {
 		return ftello(mine->f);
 	}
 #else
-	if (fseek(mine->f, skip, whence) == 0) {
+	if (fseek(mine->f, seek, whence) == 0) {
 		return ftell(mine->f);
 	}
 #endif
@@ -227,4 +230,4 @@ FILE_close(struct archive *a, void *client_data)
 	free(mine->buffer);
 	free(mine);
 	return (ARCHIVE_OK);
-}
\ No newline at end of file
+}
diff --git a/libarchive/archive_read_open_filename.c b/libarchive/archive_read_open_filename.c
index 05f0ffbd..3894b15c 100644
--- a/libarchive/archive_read_open_filename.c
+++ b/libarchive/archive_read_open_filename.c
@@ -449,20 +449,24 @@ file_skip_lseek(struct archive *a, void *client_data, int64_t request)
 	struct read_file_data *mine = (struct read_file_data *)client_data;
 #if defined(_WIN32) && !defined(__CYGWIN__)
 	/* We use _lseeki64() on Windows. */
-	int64_t old_offset, new_offset;
+	int64_t old_offset, new_offset, skip = request;
 #else
-	off_t old_offset, new_offset;
+	off_t old_offset, new_offset, skip = (off_t)request;
 #endif
+	int skip_bits = sizeof(skip) * 8 - 1;
 
 	/* We use off_t here because lseek() is declared that way. */
 
-	/* TODO: Deal with case where off_t isn't 64 bits.
-	 * This shouldn't be a problem on Linux or other POSIX
-	 * systems, since the configuration logic for libarchive
-	 * tries to obtain a 64-bit off_t.
-	 */
+	/* Reduce a request that would overflow the 'skip' variable. */
+	if (sizeof(request) > sizeof(skip)) {
+		const int64_t max_skip =
+		    (((int64_t)1 << (skip_bits - 1)) - 1) * 2 + 1;
+		if (request > max_skip)
+			skip = max_skip;
+	}
+
 	if ((old_offset = lseek(mine->fd, 0, SEEK_CUR)) >= 0 &&
-	    (new_offset = lseek(mine->fd, request, SEEK_CUR)) >= 0)
+	    (new_offset = lseek(mine->fd, skip, SEEK_CUR)) >= 0)
 		return (new_offset - old_offset);
 
 	/* If lseek() fails, don't bother trying again. */
@@ -510,11 +514,24 @@ static int64_t
 file_seek(struct archive *a, void *client_data, int64_t request, int whence)
 {
 	struct read_file_data *mine = (struct read_file_data *)client_data;
+	off_t seek = (off_t)request;
 	int64_t r;
+	int seek_bits = sizeof(seek) * 8 - 1;
 
 	/* We use off_t here because lseek() is declared that way. */
-	/* See above for notes about when off_t is less than 64 bits. */
-	r = lseek(mine->fd, request, whence);
+
+	/* Reduce a request that would overflow the 'seek' variable. */
+	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;
+	}
+
+	r = lseek(mine->fd, seek, whence);
 	if (r >= 0)
 		return r;
 
diff --git a/libarchive/test/read_open_memory.c b/libarchive/test/read_open_memory.c
index 6d2468cd..9262ab9d 100644
--- a/libarchive/test/read_open_memory.c
+++ b/libarchive/test/read_open_memory.c
@@ -168,7 +168,7 @@ memory_read_skip(struct archive *a, void *client_data, int64_t skip)
 
 	(void)a; /* UNUSED */
 	/* We can't skip by more than is available. */
-	if ((off_t)skip > (off_t)(mine->end - mine->p))
+	if (skip > mine->end - mine->p)
 		skip = mine->end - mine->p;
 	/* Always do small skips by prime amounts. */
 	if (skip > 71)
diff --git a/libarchive/test/test_sparse_basic.c b/libarchive/test/test_sparse_basic.c
index 23cde567..93710cb6 100644
--- a/libarchive/test/test_sparse_basic.c
+++ b/libarchive/test/test_sparse_basic.c
@@ -606,7 +606,8 @@ DEFINE_TEST(test_sparse_basic)
 	verify_sparse_file(a, "file2", sparse_file2, 20);
 	/* Encoded non sparse; expect a data block but no sparse entries. */
 	verify_sparse_file(a, "file3", sparse_file3, 0);
-	verify_sparse_file(a, "file4", sparse_file4, 2);
+	if (sizeof(off_t) > 4)
+		verify_sparse_file(a, "file4", sparse_file4, 2);
 
 	assertEqualInt(ARCHIVE_OK, archive_read_free(a));
 
@@ -633,7 +634,8 @@ DEFINE_TEST(test_sparse_basic)
 	verify_sparse_file(a, "file1", sparse_file1, 0);
 	verify_sparse_file(a, "file2", sparse_file2, 0);
 	verify_sparse_file(a, "file3", sparse_file3, 0);
-	verify_sparse_file(a, "file4", sparse_file4, 0);
+	if (sizeof(off_t) > 4)
+		verify_sparse_file(a, "file4", sparse_file4, 0);
 
 	assertEqualInt(ARCHIVE_OK, archive_read_free(a));
 
diff --git a/libarchive/test/test_tar_large.c b/libarchive/test/test_tar_large.c
index c1f37916..1cde3218 100644
--- a/libarchive/test/test_tar_large.c
+++ b/libarchive/test/test_tar_large.c
@@ -176,7 +176,7 @@ memory_read_skip(struct archive *a, void *_private, int64_t skip)
 	}
 	if (private->filebytes > 0) {
 		if (private->filebytes < skip)
-			skip = (off_t)private->filebytes;
+			skip = private->filebytes;
 		private->filebytes -= skip;
 	} else {
 		skip = 0;
