3.2.101-rc1 review patch. If anyone has any objections, please let me know.
------------------ From: Dan Williams <[email protected]> commit 56c30ba7b348b90484969054d561f711ba196507 upstream. 'fd' is a user controlled value that is used as a data dependency to read from the 'fdt->fd' array. In order to avoid potential leaks of kernel memory values, block speculative execution of the instruction stream that could issue reads based on an invalid 'file *' returned from __fcheck_files. Co-developed-by: Elena Reshetova <[email protected]> Signed-off-by: Dan Williams <[email protected]> Signed-off-by: Thomas Gleixner <[email protected]> Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: Al Viro <[email protected]> Cc: [email protected] Cc: [email protected] Link: https://lkml.kernel.org/r/151727418500.33451.17392199002892248656.st...@dwillia2-desk3.amr.corp.intel.com [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings <[email protected]> --- include/linux/fdtable.h | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- a/include/linux/fdtable.h +++ b/include/linux/fdtable.h @@ -9,6 +9,7 @@ #include <linux/compiler.h> #include <linux/spinlock.h> #include <linux/rcupdate.h> +#include <linux/nospec.h> #include <linux/types.h> #include <linux/init.h> #include <linux/fs.h> @@ -85,8 +86,10 @@ static inline struct file * fcheck_files struct file * file = NULL; struct fdtable *fdt = files_fdtable(files); - if (fd < fdt->max_fds) + if (fd < fdt->max_fds) { + fd = array_index_nospec(fd, fdt->max_fds); file = rcu_dereference_check_fdtable(files, fdt->fd[fd]); + } return file; }
