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Borntraeger wrote: > > > Am 06.07.26 um 14:24 schrieb Dragos Tatulea: >> >> >> On 06.07.26 12:13, Christian Borntraeger wrote: >>> >>> >>> Am 06.07.26 um 12:01 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. >>>> >>>> Calculates the input size as sizeof(in) + mtt_array_size to match the >>>> pointer and allocation size. >>>> >>>> Fixes: 0071b138d44a ("vdpa/mlx5: Create direct MKEYs in parallel") >>>> Signed-off-by: Christian Borntraeger >>>> --- >>>> drivers/vdpa/mlx5/core/mr.c | 2 +- >>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>> >>>> diff --git a/drivers/vdpa/mlx5/core/mr.c b/drivers/vdpa/mlx5/core/mr.c >>>> index 6d02ccf9eb91..03fe7f5ca412 100644 >>>> --- a/drivers/vdpa/mlx5/core/mr.c >>>> +++ b/drivers/vdpa/mlx5/core/mr.c >>>> @@ -233,7 +233,7 @@ static int create_direct_keys(struct mlx5_vdpa_dev *mvdev, struct mlx5_vdpa_mr * >>>> cmds[i].out = cmd_mem->out; >>>> cmds[i].outlen = sizeof(cmd_mem->out); >>>> cmds[i].in = cmd_mem->in; >>>> - cmds[i].inlen = struct_size(cmd_mem, mtt, mttcount); >>>> + cmds[i].inlen = sizeof(cmd_mem->in) + (mttcount * sizeof(cmd_mem->mtt[0])); >> Woops... Thanks for the catch. The fix is good. >> >>> >>> Assuming the fix is the correct fix, question is, if I should use the offset of in instead, e.g. >>> >>> cmds[i].inlen = struct_size(cmd_mem, mtt, mttcount) - offsetof(cmd_mem, in); >>> >>> to handle potential alignment and padding aspects. >>> >> Seems harder to read. Why not: >> sizeof(cmd_mem->in) + flex_array_size(cmd_mem, mtts, mttcount) ? > > Can do that. I assume we do not have any implicit holes in the structure due to alignment? In > other words, sizeof(cmd_mem->in) can never be something like 20 (and then the flex array would > start at 24 to align 8 byte elements). If thats the case I will respin with your proposal. Weeelll, I checked on a x86_64 build and there is a hole there of 16 bytes. So your second formula is indeed the way to go. Thanks, Dragos