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Message-ID: <20211025173150.GA396793@nvidia.com>
Date: Mon, 25 Oct 2021 14:31:50 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: Leon Romanovsky <leon@...nel.org>
Cc: Doug Ledford <dledford@...hat.com>, Alaa Hleihel <alaa@...dia.com>,
linux-kernel@...r.kernel.org, linux-rdma@...r.kernel.org
Subject: Re: [PATCH RESEND rdma-rc] RDMA/mlx5: Add dummy umem to IB_MR_TYPE_DM
On Tue, Oct 19, 2021 at 01:23:13PM +0300, Leon Romanovsky wrote:
> From: Alaa Hleihel <alaa@...dia.com>
>
> After the cited patch, and for the case of IB_MR_TYPE_DM that doesn't
> have a umem (even though it is a user MR), function mlx5_free_priv_descs()
> will think that it's a kernel MR, leading to wrongly accessing mr->descs
> that will get wrong values in the union which leads to attempting to
> release resources that were not allocated in the first place.
>
> For example:
> DMA-API: mlx5_core 0000:08:00.1: device driver tries to free DMA memory it has not allocated [device address=0x0000000000000000] [size=0 bytes]
> WARNING: CPU: 8 PID: 1021 at kernel/dma/debug.c:961 check_unmap+0x54f/0x8b0
> RIP: 0010:check_unmap+0x54f/0x8b0
> Call Trace:
> debug_dma_unmap_page+0x57/0x60
> mlx5_free_priv_descs+0x57/0x70 [mlx5_ib]
> mlx5_ib_dereg_mr+0x1fb/0x3d0 [mlx5_ib]
> ib_dereg_mr_user+0x60/0x140 [ib_core]
> uverbs_destroy_uobject+0x59/0x210 [ib_uverbs]
> uobj_destroy+0x3f/0x80 [ib_uverbs]
> ib_uverbs_cmd_verbs+0x435/0xd10 [ib_uverbs]
> ? uverbs_finalize_object+0x50/0x50 [ib_uverbs]
> ? lock_acquire+0xc4/0x2e0
> ? lock_acquired+0x12/0x380
> ? lock_acquire+0xc4/0x2e0
> ? lock_acquire+0xc4/0x2e0
> ? ib_uverbs_ioctl+0x7c/0x140 [ib_uverbs]
> ? lock_release+0x28a/0x400
> ib_uverbs_ioctl+0xc0/0x140 [ib_uverbs]
> ? ib_uverbs_ioctl+0x7c/0x140 [ib_uverbs]
> __x64_sys_ioctl+0x7f/0xb0
> do_syscall_64+0x38/0x90
>
> Fix it by adding a dummy umem to IB_MR_TYPE_DM MRs.
>
> Fixes: f18ec4223117 ("RDMA/mlx5: Use a union inside mlx5_ib_mr")
> Signed-off-by: Alaa Hleihel <alaa@...dia.com>
> Signed-off-by: Leon Romanovsky <leonro@...dia.com>
> RESEND: https://lore.kernel.org/all/9c6478b70dc23cfec3a7bfc345c30ff817e7e799.1631660866.git.leonro@nvidia.com
>
> Our request to drop that original patch was because mr-->umem pointer is checked
> in rereg flow for the DM MRs with expectation to have NULL there. However DM is
> blocked for the rereg path in the commit 5ccbf63f87a3 ("IB/uverbs: Prevent
> reregistration of DM_MR to regular MR"), and the checks in mlx5_ib are redundant.
That logic in the core code is bogus and should be deleted.
It is perfeclty fine to use rereg to change the access flags on a DM
MR and mlx5 now implements that.
So let's not go down a path that blocks it.
Like this instead:
diff --git a/drivers/infiniband/hw/mlx5/mlx5_ib.h b/drivers/infiniband/hw/mlx5/mlx5_ib.h
index e636e954f6bf2a..4a7a56ed740b9b 100644
--- a/drivers/infiniband/hw/mlx5/mlx5_ib.h
+++ b/drivers/infiniband/hw/mlx5/mlx5_ib.h
@@ -664,7 +664,6 @@ struct mlx5_ib_mr {
/* User MR data */
struct mlx5_cache_ent *cache_ent;
- struct ib_umem *umem;
/* This is zero'd when the MR is allocated */
union {
@@ -676,7 +675,7 @@ struct mlx5_ib_mr {
struct list_head list;
};
- /* Used only by kernel MRs (umem == NULL) */
+ /* Used only by kernel MRs */
struct {
void *descs;
void *descs_alloc;
@@ -697,8 +696,9 @@ struct mlx5_ib_mr {
int data_length;
};
- /* Used only by User MRs (umem != NULL) */
+ /* Used only by User MRs */
struct {
+ struct ib_umem *umem;
unsigned int page_shift;
/* Current access_flags */
int access_flags;
diff --git a/drivers/infiniband/hw/mlx5/mr.c b/drivers/infiniband/hw/mlx5/mr.c
index 221f0949794e35..997d133d00369d 100644
--- a/drivers/infiniband/hw/mlx5/mr.c
+++ b/drivers/infiniband/hw/mlx5/mr.c
@@ -1904,19 +1904,19 @@ mlx5_alloc_priv_descs(struct ib_device *device,
return ret;
}
-static void
-mlx5_free_priv_descs(struct mlx5_ib_mr *mr)
+static void mlx5_free_priv_descs(struct mlx5_ib_mr *mr)
{
- if (!mr->umem && mr->descs) {
- struct ib_device *device = mr->ibmr.device;
- int size = mr->max_descs * mr->desc_size;
- struct mlx5_ib_dev *dev = to_mdev(device);
+ struct ib_device *device = mr->ibmr.device;
+ int size = mr->max_descs * mr->desc_size;
+ struct mlx5_ib_dev *dev = to_mdev(device);
- dma_unmap_single(&dev->mdev->pdev->dev, mr->desc_map, size,
- DMA_TO_DEVICE);
- kfree(mr->descs_alloc);
- mr->descs = NULL;
- }
+ if (!mr->descs)
+ return;
+
+ dma_unmap_single(&dev->mdev->pdev->dev, mr->desc_map, size,
+ DMA_TO_DEVICE);
+ kfree(mr->descs_alloc);
+ mr->descs = NULL;
}
int mlx5_ib_dereg_mr(struct ib_mr *ibmr, struct ib_udata *udata)
@@ -1978,7 +1978,7 @@ int mlx5_ib_dereg_mr(struct ib_mr *ibmr, struct ib_udata *udata)
return rc;
}
- if (mr->umem) {
+ if (udata && mr->umem) {
bool is_odp = is_odp_mr(mr);
if (!is_odp)
@@ -1992,7 +1992,8 @@ int mlx5_ib_dereg_mr(struct ib_mr *ibmr, struct ib_udata *udata)
if (mr->cache_ent) {
mlx5_mr_cache_free(dev, mr);
} else {
- mlx5_free_priv_descs(mr);
+ if (!udata)
+ mlx5_free_priv_descs(mr);
kfree(mr);
}
return 0;
@@ -2079,7 +2080,6 @@ static struct mlx5_ib_mr *mlx5_ib_alloc_pi_mr(struct ib_pd *pd,
if (err)
goto err_free_in;
- mr->umem = NULL;
kfree(in);
return mr;
@@ -2206,7 +2206,6 @@ static struct ib_mr *__mlx5_ib_alloc_mr(struct ib_pd *pd,
}
mr->ibmr.device = pd->device;
- mr->umem = NULL;
switch (mr_type) {
case IB_MR_TYPE_MEM_REG:
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