4.18-stable review patch. If anyone has any objections, please let me know.
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From: Jann Horn jannh@google.com
[ Upstream commit 0d23ba6034b9cf48b8918404367506da3e4b3ee5 ]
The current code grabs the private_data of whatever file descriptor userspace has supplied and implicitly casts it to a `struct ucma_file *`, potentially causing a type confusion.
This is probably fine in practice because the pointer is only used for comparisons, it is never actually dereferenced; and even in the comparisons, it is unlikely that a file from another filesystem would have a ->private_data pointer that happens to also be valid in this context. But ->private_data is not always guaranteed to be a valid pointer to an object owned by the file's filesystem; for example, some filesystems just cram numbers in there.
Check the type of the supplied file descriptor to be safe, analogous to how other places in the kernel do it.
Fixes: 88314e4dda1e ("RDMA/cma: add support for rdma_migrate_id()") Signed-off-by: Jann Horn jannh@google.com Signed-off-by: Jason Gunthorpe jgg@mellanox.com Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/infiniband/core/ucma.c | 6 ++++++ 1 file changed, 6 insertions(+)
--- a/drivers/infiniband/core/ucma.c +++ b/drivers/infiniband/core/ucma.c @@ -124,6 +124,8 @@ static DEFINE_MUTEX(mut); static DEFINE_IDR(ctx_idr); static DEFINE_IDR(multicast_idr);
+static const struct file_operations ucma_fops; + static inline struct ucma_context *_ucma_find_context(int id, struct ucma_file *file) { @@ -1581,6 +1583,10 @@ static ssize_t ucma_migrate_id(struct uc f = fdget(cmd.fd); if (!f.file) return -ENOENT; + if (f.file->f_op != &ucma_fops) { + ret = -EINVAL; + goto file_put; + }
/* Validate current fd and prevent destruction of id. */ ctx = ucma_get_ctx(f.file->private_data, cmd.id);