3.2.101-rc1 review patch. If anyone has any objections, please let me know.
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From: Dan Williams dan.j.williams@intel.com
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 elena.reshetova@intel.com Signed-off-by: Dan Williams dan.j.williams@intel.com Signed-off-by: Thomas Gleixner tglx@linutronix.de Cc: linux-arch@vger.kernel.org Cc: kernel-hardening@lists.openwall.com Cc: gregkh@linuxfoundation.org Cc: Al Viro viro@zeniv.linux.org.uk Cc: torvalds@linux-foundation.org Cc: alan@linux.intel.com Link: https://lkml.kernel.org/r/151727418500.33451.17392199002892248656.stgit@dwil... [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- 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; }