[tip: x86/sgx] x86/sgx: Return -EINVAL on a zero length buffer in sgx_ioc_enclave_add_pages()

[tip-bot2 for Jarkko Sakkinen]

The following commit has been merged into the x86/sgx branch of tip:

Commit-ID:     a4b9c48b96517ff4780b22a784e7537eac5dc21b
Gitweb:        https://git.kernel.org/tip/a4b9c48b96517ff4780b22a784e7537eac5dc21b
Author:        Jarkko Sakkinen <jarkko@xxxxxxxxxx>
AuthorDate:    Thu, 03 Dec 2020 20:35:27 +02:00
Committer:     Borislav Petkov <bp@xxxxxxx>
CommitterDate: Thu, 03 Dec 2020 19:54:40 +01:00

x86/sgx: Return -EINVAL on a zero length buffer in sgx_ioc_enclave_add_pages()

The sgx_enclave_add_pages.length field is documented as

 * @length:     length of the data (multiple of the page size)

Fail with -EINVAL, when the caller gives a zero length buffer of data
to be added as pages to an enclave. Right now 'ret' is returned as
uninitialized in that case.

 [ bp: Flesh out commit message. ]

Fixes: c6d26d370767 ("x86/sgx: Add SGX_IOC_ENCLAVE_ADD_PAGES")
Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Signed-off-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Link: https://lore.kernel.org/linux-sgx/X8ehQssnslm194ld@mwanda/
Link: https://lkml.kernel.org/r/20201203183527.139317-1-jarkko@xxxxxxxxxx
---
 arch/x86/kernel/cpu/sgx/ioctl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c b/arch/x86/kernel/cpu/sgx/ioctl.c
index c206aee..90a5caf 100644
--- a/arch/x86/kernel/cpu/sgx/ioctl.c
+++ b/arch/x86/kernel/cpu/sgx/ioctl.c
@@ -428,7 +428,7 @@ static long sgx_ioc_enclave_add_pages(struct sgx_encl *encl, void __user *arg)
 	    !IS_ALIGNED(add_arg.src, PAGE_SIZE))
 		return -EINVAL;
 
-	if (add_arg.length & (PAGE_SIZE - 1))
+	if (!add_arg.length || add_arg.length & (PAGE_SIZE - 1))
 		return -EINVAL;
 
 	if (add_arg.offset + add_arg.length - PAGE_SIZE >= encl->size)