[PATCH] powerpc/pseries: Fix endianness issue when parsing PLPKS secvar flags

When a user updates a variable through the PLPKS secvar interface, we take
the first 8 bytes of the data written to the update attribute to pass
through to the H_PKS_SIGNED_UPDATE hcall as flags. These bytes are always
written in big-endian format.

Currently, the flags bytes are memcpy()ed into a u64, which is then loaded
into a register to pass as part of the hcall. This means that on LE
systems, the bytes are in the wrong order.

Use be64_to_cpup() instead, to ensure the flags bytes are byteswapped if
necessary.

Reported-by: Stefan Berger <stefanb@linux.ibm.com>
Fixes: ccadf154cb00 ("powerpc/pseries: Implement secvars for dynamic secure boot")
Signed-off-by: Andrew Donnellan <redacted>
---
 arch/powerpc/platforms/pseries/plpks-secvar.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/platforms/pseries/plpks-secvar.c b/arch/powerpc/platforms/pseries/plpks-secvar.c
index f6c8888f4076..257fd1f8bc19 100644
--- a/arch/powerpc/platforms/pseries/plpks-secvar.c
+++ b/arch/powerpc/platforms/pseries/plpks-secvar.c

@@ -135,7 +135,8 @@ static int plpks_set_variable(const char *key, u64 key_len, u8 *data,
 		goto err;
 	var.namelen = rc * 2;
 
-	memcpy(&flags, data, sizeof(flags));
+	// Flags are contained in the first 8 bytes of the buffer, and are always big-endian
+	flags = be64_to_cpup((__be64 *)data);
 
 	var.datalen = data_size - sizeof(flags);
 	var.data = data + sizeof(flags);

-- 
2.39.1

On Thu, 16 Feb 2023 18:09:03 +1100, Andrew Donnellan wrote:

When a user updates a variable through the PLPKS secvar interface, we take
the first 8 bytes of the data written to the update attribute to pass
through to the H_PKS_SIGNED_UPDATE hcall as flags. These bytes are always
written in big-endian format.

Currently, the flags bytes are memcpy()ed into a u64, which is then loaded
into a register to pass as part of the hcall. This means that on LE
systems, the bytes are in the wrong order.

[...]

Applied to powerpc/next.

[1/1] powerpc/pseries: Fix endianness issue when parsing PLPKS secvar flags
      https://git.kernel.org/powerpc/c/7096deb7b5387e7899655213b7430ab043ddda4f

cheers