On Tue, Mar 17, 2020 at 7:38 AM Catalin Marinas [off-list ref] wrote:

On Tue, Mar 17, 2020 at 12:22:12PM +0000, Vincenzo Frascino wrote:

quoted

diff --git a/arch/arm64/kernel/vdso32/vgettimeofday.c b/arch/arm64/kernel/vdso32/vgettimeofday.c
index 54fc1c2ce93f..91138077b073 100644
--- a/arch/arm64/kernel/vdso32/vgettimeofday.c
+++ b/arch/arm64/kernel/vdso32/vgettimeofday.c

@@ -8,11 +8,14 @@
 #include <linux/time.h>
 #include <linux/types.h>

+#define VALID_CLOCK_ID(x) \
+     ((x >= 0) && (x < VDSO_BASES))
+
 int __vdso_clock_gettime(clockid_t clock,
                       struct old_timespec32 *ts)
 {
      /* The checks below are required for ABI consistency with arm */
-     if ((u32)ts >= TASK_SIZE_32)
+     if ((u32)ts > UINTPTR_MAX - sizeof(*ts) + 1)
              return -EFAULT;

      return __cvdso_clock_gettime32(clock, ts);

I probably miss something but I can't find the TASK_SIZE check in the
arch/arm/vdso/vgettimeofday.c code. Is this done elsewhere?

Can you not just remove the TASK_SIZE_32 check entirely?  If you pass
a garbage address to the vDSO, you are quite likely to get SIGSEGV.
Why does this particular type of error need special handling?

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