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 Cc: [email protected] Signed-off-by: Gustavo A. R. Silva <[email protected]> --- kernel/sys.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/kernel/sys.c b/kernel/sys.c index 63ef036..78646e6 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -69,6 +69,9 @@ #include <asm/io.h> #include <asm/unistd.h> +/* Hardening for Spectre-v1 */ +#include <linux/nospec.h> + #include "uid16.h" #ifndef SET_UNALIGN_CTL @@ -1451,6 +1454,7 @@ SYSCALL_DEFINE2(old_getrlimit, unsigned int, resource, 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); @@ -1470,6 +1474,7 @@ COMPAT_SYSCALL_DEFINE2(old_getrlimit, unsigned int, resource, if (resource >= RLIM_NLIMITS) return -EINVAL; + resource = array_index_nospec(resource, RLIM_NLIMITS); task_lock(current->group_leader); r = current->signal->rlim[resource]; task_unlock(current->group_leader); -- 2.7.4
