4.4-stable review patch. If anyone has any objections, please let me know.
------------------ From: Gustavo A. R. Silva <[email protected]> commit 23d6aef74da86a33fa6bb75f79565e0a16ee97c2 upstream. `resource' can be controlled by user-space, hence leading to a potential exploitation of the Spectre variant 1 vulnerability. This issue was detected with the help of Smatch: kernel/sys.c:1474 __do_compat_sys_old_getrlimit() warn: potential spectre issue 'get_current()->signal->rlim' (local cap) kernel/sys.c:1455 __do_sys_old_getrlimit() warn: potential spectre issue 'get_current()->signal->rlim' (local cap) Fix this by sanitizing *resource* before using it to index current->signal->rlim Notice that given that speculation windows are large, the policy is to kill the speculation on the first load and not worry if it can be completed with a dependent load/store [1]. [1] https://marc.info/?l=linux-kernel&m=152449131114778&w=2 Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Gustavo A. R. Silva <[email protected]> Reviewed-by: Andrew Morton <[email protected]> Cc: Alexei Starovoitov <[email protected]> Cc: Dan Williams <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- kernel/sys.c | 3 +++ 1 file changed, 3 insertions(+) --- a/kernel/sys.c +++ b/kernel/sys.c @@ -53,6 +53,8 @@ #include <linux/uidgid.h> #include <linux/cred.h> +#include <linux/nospec.h> + #include <linux/kmsg_dump.h> /* Move somewhere else to avoid recompiling? */ #include <generated/utsrelease.h> @@ -1311,6 +1313,7 @@ SYSCALL_DEFINE2(old_getrlimit, unsigned if (resource >= RLIM_NLIMITS) return -EINVAL; + resource = array_index_nospec(resource, RLIM_NLIMITS); task_lock(current->group_leader); x = current->signal->rlim[resource]; task_unlock(current->group_leader);
