Re: [PATCH v3] vdpa/mlx5: Fix buffer length in create_direct_keys()

[Christian Borntraeger <borntraeger@linux.ibm.com>]

Am 06.07.26 um 16:15 schrieb Christian Borntraeger:
> We have seen in our CI the following KASAN message:
> BUG: KASAN: slab-out-of-bounds in cmd_exec+0x550/0xca0 [mlx5_core]
> Read of size 272 at addr 0000000176795020 by task qemu-system-s39/82764
> [...]
> [<000011388ab3a7a0>] cmd_exec+0x550/0xca0 [mlx5_core]
> [<000011388ab3b61c>] mlx5_cmd_exec_cb+0x25c/0x4f0 [mlx5_core]
> [<000011388b21e82e>] mlx5_vdpa_exec_async_cmds+0x22e/0x5e0 [mlx5_vdpa]
> [<000011388b21fd44>] create_direct_keys+0x954/0xef0 [mlx5_vdpa]
> [...]
> The buggy address is located 4128 bytes inside of
> allocated 4384-byte region [0000000176794000, 0000000176795120)
> 
> So in essence we read 16 bytes beyond 4384-byte allocation.
> create_direct_keys calculates the pointer and length for in and out
> buffers.
> The size calculation for in includes the entire structure
> size (out + in + mtt[]) but the pointer passed to cmd_exec points only
> to the 'in' field, skipping the 'out' field.
> 
> This causes mlx5_copy_to_msg() to read beyond the allocated buffer
> by sizeof(out) bytes when copying command data.
> 
> Properly calculate the input size to match the pointer and allocation size.
> 
> Fixes: 0071b138d44a ("vdpa/mlx5: Create direct MKEYs in parallel")
> Signed-off-by: Christian Borntraeger <borntraeger@linux.ibm.com>


Dragos,

With this fix our nighly CI did not result in a kasan message. As I only have
limited test coverage a full regression on your side might still be the right
thing to do.