6.1-stable review patch. If anyone has any objections, please let me know.
------------------
From: Ondrej Mosnacek <omosnace@xxxxxxxxxx>
commit b36995b8609a5a8fe5cf259a1ee768fcaed919f8 upstream.
-EOPNOTSUPP is the return value that implements a "no-op" hook, not 0.
Without this fix having only the BPF LSM enabled (with no programs
attached) can cause uninitialized variable reads in
nfsd4_encode_fattr(), because the BPF hook returns 0 without touching
the 'ctxlen' variable and the corresponding 'contextlen' variable in
nfsd4_encode_fattr() remains uninitialized, yet being treated as valid
based on the 0 return value.
Cc: stable@xxxxxxxxxxxxxxx
Fixes: 98e828a0650f ("security: Refactor declaration of LSM hooks")
Reported-by: Benjamin Coddington <bcodding@xxxxxxxxxx>
Signed-off-by: Ondrej Mosnacek <omosnace@xxxxxxxxxx>
Signed-off-by: Paul Moore <paul@xxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
include/linux/lsm_hook_defs.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -266,7 +266,7 @@ LSM_HOOK(void, LSM_RET_VOID, release_sec
LSM_HOOK(void, LSM_RET_VOID, inode_invalidate_secctx, struct inode *inode)
LSM_HOOK(int, 0, inode_notifysecctx, struct inode *inode, void *ctx, u32 ctxlen)
LSM_HOOK(int, 0, inode_setsecctx, struct dentry *dentry, void *ctx, u32 ctxlen)
-LSM_HOOK(int, 0, inode_getsecctx, struct inode *inode, void **ctx,
+LSM_HOOK(int, -EOPNOTSUPP, inode_getsecctx, struct inode *inode, void **ctx,
u32 *ctxlen)
#if defined(CONFIG_SECURITY) && defined(CONFIG_WATCH_QUEUE)
