[PATCH 3.16 214/410] pipe: reject F_SETPIPE_SZ with size over UINT_MAX

[Ben Hutchings]

3.16.57-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Biggers <ebiggers@xxxxxxxxxx>

commit 96e99be40e4cff870a83233731121ec0f7f95075 upstream.

A pipe's size is represented as an 'unsigned int'.  As expected, writing a
value greater than UINT_MAX to /proc/sys/fs/pipe-max-size fails with
EINVAL.  However, the F_SETPIPE_SZ fcntl silently truncates such values to
32 bits, rather than failing with EINVAL as expected.  (It *does* fail
with EINVAL for values above (1 << 31) but <= UINT_MAX.)

Fix this by moving the check against UINT_MAX into round_pipe_size() which
is called in both cases.

Link: http://lkml.kernel.org/r/20180111052902.14409-6-ebiggers3@xxxxxxxxx
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
Acked-by: Kees Cook <keescook@xxxxxxxxxxxx>
Acked-by: Joe Lawrence <joe.lawrence@xxxxxxxxxx>
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: "Luis R . Rodriguez" <mcgrof@xxxxxxxxxx>
Cc: Michael Kerrisk <mtk.manpages@xxxxxxxxx>
Cc: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Cc: Willy Tarreau <w@xxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 fs/pipe.c                 | 5 ++++-
 include/linux/pipe_fs_i.h | 2 +-
 kernel/sysctl.c           | 3 ---
 3 files changed, 5 insertions(+), 5 deletions(-)

--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -1008,10 +1008,13 @@ const struct file_operations pipefifo_fo
  * Currently we rely on the pipe array holding a power-of-2 number
  * of pages. Returns 0 on error.
  */
-unsigned int round_pipe_size(unsigned int size)
+unsigned int round_pipe_size(unsigned long size)
 {
 	unsigned long nr_pages;
 
+	if (size > UINT_MAX)
+		return 0;
+
 	/* Minimum pipe size, as required by POSIX */
 	if (size < PAGE_SIZE)
 		size = PAGE_SIZE;
--- a/include/linux/pipe_fs_i.h
+++ b/include/linux/pipe_fs_i.h
@@ -148,6 +148,6 @@ long pipe_fcntl(struct file *, unsigned
 struct pipe_inode_info *get_pipe_info(struct file *file);
 
 int create_pipe_files(struct file **, int);
-unsigned int round_pipe_size(unsigned int size);
+unsigned int round_pipe_size(unsigned long size);
 
 #endif
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -2230,9 +2230,6 @@ static int do_proc_dopipe_max_size_conv(
 	if (write) {
 		unsigned int val;
 
-		if (*lvalp > UINT_MAX)
-			return -EINVAL;
-
 		val = round_pipe_size(*lvalp);
 		if (*negp || val == 0)
 			return -EINVAL;