On Wed, Apr 14, 2021 at 02:06:43PM +0800, Jisheng Zhang wrote:

I met below error during boot with i915 builtin if pass "i915.mitigations=off": [ 0.015589] Booting kernel: `off' invalid for parameter `i915.mitigations'

The reason is slab subsystem isn't ready at that time, so kstrdup() returns NULL. Fix this issue by using stack var instead of kstrdup().

Fixes: 984cadea032b ("drm/i915: Allow the sysadmin to override security mitigations") Signed-off-by: Jisheng Zhang Jisheng.Zhang@synaptics.com

---

Since v1:

• Ensure "str" is properly terminated. Thanks Ville for pointing this out.

drivers/gpu/drm/i915/i915_mitigations.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_mitigations.c b/drivers/gpu/drm/i915/i915_mitigations.c index 84f12598d145..231aad5ff46c 100644 --- a/drivers/gpu/drm/i915/i915_mitigations.c +++ b/drivers/gpu/drm/i915/i915_mitigations.c @@ -29,15 +29,14 @@ bool i915_mitigate_clear_residuals(void) static int mitigations_set(const char *val, const struct kernel_param *kp) { unsigned long new = ~0UL;

• char *str, *sep, *tok;

• char str[64], *sep, *tok; bool first = true; int err = 0;

  BUILD_BUG_ON(ARRAY_SIZE(names) >= BITS_PER_TYPE(mitigations));

• str = kstrdup(val, GFP_KERNEL);
• if (!str)

• return -ENOMEM;
  

• strncpy(str, val, sizeof(str) - 1);
• str[sizeof(str) - 1] = '\0';

Looks correct, however strscpy() seems to be the thing we should be using these days.

for (sep = str; (tok = strsep(&sep, ","));) { bool enable = true; @@ -86,7 +85,6 @@ static int mitigations_set(const char *val, const struct kernel_param *kp) break; } }

• kfree(str); if (err) return err;

-- 2.31.0