Re: [PATCH 3/8] drm/amdkfd: fix overflow for the function criu_restore_bos

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On 2024-05-29 23:47, Jesse Zhang wrote:
When copying the information from the user fails, it will goto exit.
But the variable i remains at 0, and do i-- will overflow.

i-- may underflow, but the loop will still exit. Why is the underflow a problem?



Signed-off-by: Jesse Zhang <Jesse.Zhang@xxxxxxx>
---
  drivers/gpu/drm/amd/amdkfd/kfd_chardev.c | 3 ++-
  1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c b/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
index fdf171ad4a3c..dac8fdc49e3b 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
@@ -2480,10 +2480,11 @@ static int criu_restore_bos(struct kfd_process *p,
  		ret = -EFAULT;
exit:
-	while (ret && i--) {
+	while (ret && i) {
  		if (bo_buckets[i].alloc_flags
  		   & (KFD_IOC_ALLOC_MEM_FLAGS_VRAM | KFD_IOC_ALLOC_MEM_FLAGS_GTT))
  			close_fd(bo_buckets[i].dmabuf_fd);
+		i--;

This changes the value of i in the loop body. To get the same behaviour you'd need to decrement i at the start of the loop body.

Regards,
  Felix


  	}
  	kvfree(bo_buckets);
  	kvfree(bo_privs);



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