[PATCH] ntfs3: harden against integer overflows

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Smatch complains that the "add_bytes" is not to be trusted.  Use
size_add() to prevent an integer overflow.

Fixes: be71b5cba2e6 ("fs/ntfs3: Add attrib operations")
Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
---
The add_bytes variable comes from:

	add = ALIGN(struct_size(ea_all, name, 1 + name_len + val_size), 4);

This is problematic and has inspired a new static checker warning:

fs/ntfs3/xattr.c:26 unpacked_ea_size() warn: using integer overflow function 'size_add()' for math
fs/ntfs3/xattr.c:290 ntfs_set_ea() warn: using integer overflow function 'size_add()' for math

The issue is that the struct_size() has an integer overflow and we call
ALIGN() on it, then "add" becomes zero.  Is there a bounds check that
we could use here?

	add = struct_size(ea_all, name, 1 + name_len + val_size);
	if (add > SOMETHING_MAX)
		return -EINVAL;

Otherwise the limit would have to be if (add > ULONG_MAX - 3) { which
is ugly.

 fs/ntfs3/xattr.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ntfs3/xattr.c b/fs/ntfs3/xattr.c
index 7de8718c68a9..ea582b4fe1d9 100644
--- a/fs/ntfs3/xattr.c
+++ b/fs/ntfs3/xattr.c
@@ -107,7 +107,7 @@ static int ntfs_read_ea(struct ntfs_inode *ni, struct EA_FULL **ea,
 		return -EFBIG;
 
 	/* Allocate memory for packed Ea. */
-	ea_p = kmalloc(size + add_bytes, GFP_NOFS);
+	ea_p = kmalloc(size_add(size, add_bytes), GFP_NOFS);
 	if (!ea_p)
 		return -ENOMEM;
 
-- 
2.35.1




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