path: root/tools/testing/selftests/x86
diff options
authorAndy Lutomirski <luto@kernel.org>2019-11-20 11:58:32 -0800
committerPeter Zijlstra <peterz@infradead.org>2019-11-21 21:55:59 +0100
commit4d2fa82d98d2d296043a04eb517d7dbade5b13b8 (patch)
tree22cbeb0e35d67cd39a7b3d9bdb8550e3d535f322 /tools/testing/selftests/x86
parentselftests/x86/mov_ss_trap: Fix the SYSENTER test (diff)
selftests/x86/sigreturn/32: Invalidate DS and ES when abusing the kernel
If the kernel accidentally uses DS or ES while the user values are loaded, it will work fine for sane userspace. In the interest of simulating maximally insane userspace, make sigreturn_32 zero out DS and ES for the nasty parts so that inadvertent use of these segments will crash. Signed-off-by: Andy Lutomirski <luto@kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: stable@kernel.org
Diffstat (limited to 'tools/testing/selftests/x86')
1 files changed, 13 insertions, 0 deletions
diff --git a/tools/testing/selftests/x86/sigreturn.c b/tools/testing/selftests/x86/sigreturn.c
index 3e49a7873f3e..57c4f67f16ef 100644
--- a/tools/testing/selftests/x86/sigreturn.c
+++ b/tools/testing/selftests/x86/sigreturn.c
@@ -451,6 +451,19 @@ static void sigusr1(int sig, siginfo_t *info, void *ctx_void)
ctx->uc_mcontext.gregs[REG_SP] = (unsigned long)0x8badf00d5aadc0deULL;
ctx->uc_mcontext.gregs[REG_CX] = 0;
+#ifdef __i386__
+ /*
+ * Make sure the kernel doesn't inadvertently use DS or ES-relative
+ * accesses in a region where user DS or ES is loaded.
+ *
+ * Skip this for 64-bit builds because long mode doesn't care about
+ * DS and ES and skipping it increases test coverage a little bit,
+ * since 64-bit kernels can still run the 32-bit build.
+ */
+ ctx->uc_mcontext.gregs[REG_DS] = 0;
+ ctx->uc_mcontext.gregs[REG_ES] = 0;
memcpy(&requested_regs, &ctx->uc_mcontext.gregs, sizeof(gregset_t));
requested_regs[REG_CX] = *ssptr(ctx); /* The asm code does this. */