4.14-stable review patch. If anyone has any objections, please let me know.
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From: Gustavo A. R. Silva gustavo@embeddedor.com
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/20180515030038.GA11822@embeddedor.com Signed-off-by: Gustavo A. R. Silva gustavo@embeddedor.com Reviewed-by: Andrew Morton akpm@linux-foundation.org Cc: Alexei Starovoitov ast@kernel.org Cc: Dan Williams dan.j.williams@intel.com Cc: Thomas Gleixner tglx@linutronix.de Cc: Peter Zijlstra peterz@infradead.org Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- kernel/sys.c | 2 ++ 1 file changed, 2 insertions(+)
--- a/kernel/sys.c +++ b/kernel/sys.c @@ -1395,6 +1395,7 @@ 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); @@ -1414,6 +1415,7 @@ COMPAT_SYSCALL_DEFINE2(old_getrlimit, un 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);