The patch titled Subject: kernel/sys.c: fix potential Spectre v1 issue has been added to the -mm tree. Its filename is kernel-sys-fix-potential-spectre-v1.patch
This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/kernel-sys-fix-potential-spectre-v1... and later at http://ozlabs.org/~akpm/mmotm/broken-out/kernel-sys-fix-potential-spectre-v1...
Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated there every 3-4 working days
------------------------------------------------------ From: "Gustavo A. R. Silva" gustavo@embeddedor.com Subject: kernel/sys.c: fix potential Spectre v1 issue
`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 ---
kernel/sys.c | 5 +++++ 1 file changed, 5 insertions(+)
diff -puN kernel/sys.c~kernel-sys-fix-potential-spectre-v1 kernel/sys.c --- a/kernel/sys.c~kernel-sys-fix-potential-spectre-v1 +++ a/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 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, 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); _
Patches currently in -mm which might be from gustavo@embeddedor.com are
kernel-sys-fix-potential-spectre-v1.patch