From: Matthew Wilcox <willy@xxxxxxxxxxxxx> Subject: autofs: harden ioctl table The table of ioctl functions should be marked const in order to put them in read-only memory, and we should use array_index_nospec() to avoid speculation disclosing the contents of kernel memory to userspace. Link: https://lkml.kernel.org/r/20200818122203.GO17456@xxxxxxxxxxxxxxxxxxxx Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> Acked-by: Ian Kent <raven@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/autofs/dev-ioctl.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) --- a/fs/autofs/dev-ioctl.c~harden-autofs-ioctl-table +++ a/fs/autofs/dev-ioctl.c @@ -8,6 +8,7 @@ #include <linux/compat.h> #include <linux/syscalls.h> #include <linux/magic.h> +#include <linux/nospec.h> #include "autofs_i.h" @@ -563,7 +564,7 @@ out: static ioctl_fn lookup_dev_ioctl(unsigned int cmd) { - static ioctl_fn _ioctls[] = { + static const ioctl_fn _ioctls[] = { autofs_dev_ioctl_version, autofs_dev_ioctl_protover, autofs_dev_ioctl_protosubver, @@ -581,7 +582,10 @@ static ioctl_fn lookup_dev_ioctl(unsigne }; unsigned int idx = cmd_idx(cmd); - return (idx >= ARRAY_SIZE(_ioctls)) ? NULL : _ioctls[idx]; + if (idx >= ARRAY_SIZE(_ioctls)) + return NULL; + idx = array_index_nospec(idx, ARRAY_SIZE(_ioctls)); + return _ioctls[idx]; } /* ioctl dispatcher */ _
