From: Eric Biggers <ebiggers@google.com>
Date: Fri, 7 Sep 2018 19:16:24 +0000 (-0700)
Subject: vfs: require i_size <= SIZE_MAX in kernel_read_file()
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=691115c3513ec83edf68ba6575ae85630bc94b8b;p=linux.git

vfs: require i_size <= SIZE_MAX in kernel_read_file()

On 32-bit systems, the buffer allocated by kernel_read_file() is too
small if the file size is > SIZE_MAX, due to truncation to size_t.

Fortunately, since the 'count' argument to kernel_read() is also
truncated to size_t, only the allocated space is filled; then, -EIO is
returned since 'pos != i_size' after the read loop.

But this is not obvious and seems incidental.  We should be more
explicit about this case.  So, fail early if i_size > SIZE_MAX.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
---

diff --git a/fs/exec.c b/fs/exec.c
index 1ebf6e5a521d9..fc281b738a982 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -908,14 +908,14 @@ int kernel_read_file(struct file *file, void **buf, loff_t *size,
 		goto out;
 
 	i_size = i_size_read(file_inode(file));
-	if (max_size > 0 && i_size > max_size) {
-		ret = -EFBIG;
-		goto out;
-	}
 	if (i_size <= 0) {
 		ret = -EINVAL;
 		goto out;
 	}
+	if (i_size > SIZE_MAX || (max_size > 0 && i_size > max_size)) {
+		ret = -EFBIG;
+		goto out;
+	}
 
 	if (id != READING_FIRMWARE_PREALLOC_BUFFER)
 		*buf = vmalloc(i_size);