From 59f388a67f9319d79d123a42feecf8a6efba764e Mon Sep 17 00:00:00 2001
From: Jakub Jermar <jakub@jermar.eu>
Date: Tue, 4 Apr 2017 22:56:47 +0200
Subject: [PATCH] Fail legacy interfaces if the position is too large for them
 to represent

HelenOS interfaces support unsigned 64-bit file sizes and offsets. This
is in contrast with C99-ish and POSIX-ish interfaces in libc and libposix.
The legacy API emulation internally uses the native unsigned 64-bit file
sizes and positions and so it may happen that a returned file size or
offset are bigger than the legacy interface can represent. We choose
to report failure in such a case in order to avoid returning wrong
results.
---
 uspace/lib/c/generic/io/io.c       |  4 ++++
 uspace/lib/posix/source/sys/stat.c | 17 ++++++++++++-----
 uspace/lib/posix/source/unistd.c   |  5 +++++
 3 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/uspace/lib/c/generic/io/io.c b/uspace/lib/c/generic/io/io.c
index d55c71052..274497e0b 100644
--- a/uspace/lib/c/generic/io/io.c
+++ b/uspace/lib/c/generic/io/io.c
@@ -833,6 +833,10 @@ int fseek(FILE *stream, off64_t offset, int whence)
 
 off64_t ftell(FILE *stream)
 {
+	/* The native position is too large for the C99-ish interface. */
+	if (stream->pos - stream->ungetc_chars > INT64_MAX)
+		return EOF;
+
 	if (stream->error)
 		return EOF;
 	
diff --git a/uspace/lib/posix/source/sys/stat.c b/uspace/lib/posix/source/sys/stat.c
index a257bb3c4..c16c98352 100644
--- a/uspace/lib/posix/source/sys/stat.c
+++ b/uspace/lib/posix/source/sys/stat.c
@@ -48,8 +48,10 @@
  *
  * @param dest POSIX stat struct.
  * @param src HelenOS stat struct.
+ *
+ * @return 0 on success, -1 on error.
  */
-static void stat_to_posix(struct posix_stat *dest, struct stat *src)
+static int stat_to_posix(struct posix_stat *dest, struct stat *src)
 {
 	memset(dest, 0, sizeof(struct posix_stat));
 	
@@ -67,6 +69,13 @@ static void stat_to_posix(struct posix_stat *dest, struct stat *src)
 	
 	dest->st_nlink = src->lnkcnt;
 	dest->st_size = src->size;
+
+	if (src->size > INT64_MAX) {
+		errno = ERANGE;
+		return -1;
+	}
+
+	return 0;
 }
 
 /**
@@ -82,8 +91,7 @@ int posix_fstat(int fd, struct posix_stat *st)
 	int rc = rcerrno(vfs_stat, fd, &hst);
 	if (rc < 0)
 		return -1;
-	stat_to_posix(st, &hst);
-	return 0;
+	return stat_to_posix(st, &hst);
 }
 
 /**
@@ -112,8 +120,7 @@ int posix_stat(const char *restrict path, struct posix_stat *restrict st)
 	int rc = rcerrno(vfs_stat_path, path, &hst);
 	if (rc < 0)
 		return -1;
-	stat_to_posix(st, &hst);
-	return 0;
+	return stat_to_posix(st, &hst);
 }
 
 /**
diff --git a/uspace/lib/posix/source/unistd.c b/uspace/lib/posix/source/unistd.c
index 07d1cb80a..1b1bc1788 100644
--- a/uspace/lib/posix/source/unistd.c
+++ b/uspace/lib/posix/source/unistd.c
@@ -244,6 +244,11 @@ posix_off_t posix_lseek(int fildes, posix_off_t offset, int whence)
 		posix_pos[fildes] = st.size + offset;
 		break;
 	}
+	if (posix_pos[fildes] > INT64_MAX) {
+		/* The native width is too large for the POSIX interface. */
+		errno = ERANGE;
+		return -1;
+	}
 	return posix_pos[fildes];
 }
 
-- 
2.11.4.GIT