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From: Eric Biggers <ebiggers@kernel.org>
To: linux-fsdevel@vger.kernel.org, Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Mimi Zohar <zohar@linux.vnet.ibm.com>,
	Dmitry Kasatkin <dmitry.kasatkin@huawei.com>
Subject: [PATCH] vfs: require i_size <= SIZE_MAX in kernel_read_file()
Date: Fri,  7 Sep 2018 12:16:24 -0700	[thread overview]
Message-ID: <20180907191624.186623-1-ebiggers@kernel.org> (raw)

From: Eric Biggers <ebiggers@google.com>

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>
---
 fs/exec.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/exec.c b/fs/exec.c
index 1ebf6e5a521d..fc281b738a98 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);
-- 
2.19.0.rc2.392.g5ba43deb5a-goog

             reply	other threads:[~2018-09-07 23:59 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-07 19:16 Eric Biggers [this message]
2018-09-21 18:42 ` Mimi Zohar
2018-10-03 23:43 ` Eric Biggers

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