The kernfs_fop_mmap() invokes the '->mmap' callback without verifying its existence. This leads to a NULL pointer dereference when the kernfs node does not define the operation, resulting in an invalid memory access.

Add a check to ensure the '->mmap' callback is present before invocation. Return -EINVAL when uninitialized to prevent the invalid access.

Fixes: 324a56e16e44 ("kernfs: s/sysfs_dirent/kernfs_node/ and rename its friends accordingly") Cc: stable@vger.kernel.org # 3.14+ Signed-off-by: Wentao Liang vulab@iscas.ac.cn --- fs/kernfs/file.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c index 8502ef68459b..7d8434a97487 100644 --- a/fs/kernfs/file.c +++ b/fs/kernfs/file.c @@ -459,9 +459,14 @@ static int kernfs_fop_mmap(struct file *file, struct vm_area_struct *vma) goto out_unlock;

ops = kernfs_ops(of->kn); - rc = ops->mmap(of, vma); - if (rc) + if (ops->mmap) { + rc = ops->mmap(of, vma); + if (rc) + goto out_put; + } else { + rc = -EINVAL; goto out_put; + }

/* * PowerPC's pci_mmap of legacy_mem uses shmem_zero_setup()