drm/nouveau/secboot/acr: Remove VLA usage

In the quest to remove all stack VLA usage from the kernel[1], this allocates the working buffers before starting the writing so it won't abort in the middle. This needs an initial walk of the lists to figure out how large the buffer should be.

[1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com

Signed-off-by Kees Cook <[email protected]>

---
 .../nouveau/nvkm/subdev/secboot/acr_r352.c    | 25 ++++++++++++++++---
 .../nouveau/nvkm/subdev/secboot/acr_r367.c    | 16 +++++++++++-
 2 files changed, 37 insertions(+), 4 deletions(-)

drivers/gpu/drm/nouveau/nvkm/subdev/secboot/acr_r352.c +22 -3

index a721354249ce..d02e183717dc 100644
@@ -414,6 +414,20 @@ acr_r352_ls_write_wpr(struct acr_r352 *acr, struct list_head *imgs,
 {
        struct ls_ucode_img *_img;
        u32 pos = 0;
+       u32 max_desc_size = 0;
+       u8 *gdesc;
+
+       /* Figure out how large we need gdesc to be. */
+       list_for_each_entry(_img, imgs, node) {
+               const struct acr_r352_ls_func *ls_func =
+                                           acr->func->ls_func[_img->falcon_id];
+
+               max_desc_size = max(max_desc_size, ls_func->bl_desc_size);
+       }
+
+       gdesc = kmalloc(max_desc_size, GFP_KERNEL);
+       if (!gdesc)
+               return -ENOMEM;
 
        nvkm_kmap(wpr_blob);
 

@@ -421,7 +435,6 @@ acr_r352_ls_write_wpr(struct acr_r352 *acr, struct list_head *imgs,
                struct ls_ucode_img_r352 *img = ls_ucode_img_r352(_img);
                const struct acr_r352_ls_func *ls_func =
                                            acr->func->ls_func[_img->falcon_id];
-               u8 gdesc[ls_func->bl_desc_size];
 
                nvkm_gpuobj_memcpy_to(wpr_blob, pos, &img->wpr_header,
                                      sizeof(img->wpr_header));

@@ -447,6 +460,8 @@ acr_r352_ls_write_wpr(struct acr_r352 *acr, struct list_head *imgs,
 
        nvkm_done(wpr_blob);
 
+       kfree(gdesc);
+
        return 0;
 }
 

@@ -771,7 +786,11 @@ acr_r352_load(struct nvkm_acr *_acr, struct nvkm_falcon *falcon,
        struct fw_bl_desc *hsbl_desc;
        void *bl, *blob_data, *hsbl_code, *hsbl_data;
        u32 code_size;
-       u8 bl_desc[bl_desc_size];
+       u8 *bl_desc;
+
+       bl_desc = kzalloc(bl_desc_size, GFP_KERNEL);
+       if (!bl_desc)
+               return -ENOMEM;
 
        /* Find the bootloader descriptor for our blob and copy it */
        if (blob == acr->load_blob) {

@@ -802,7 +821,6 @@ acr_r352_load(struct nvkm_acr *_acr, struct nvkm_falcon *falcon,
                              code_size, hsbl_desc->start_tag, 0, false);
 
        /* Generate the BL header */
-       memset(bl_desc, 0, bl_desc_size);
        acr->func->generate_hs_bl_desc(load_hdr, bl_desc, offset);
 
        /*

@@ -811,6 +829,7 @@ acr_r352_load(struct nvkm_acr *_acr, struct nvkm_falcon *falcon,
        nvkm_falcon_load_dmem(falcon, bl_desc, hsbl_desc->dmem_load_off,
                              bl_desc_size, 0);
 
+       kfree(bl_desc);
        return hsbl_desc->start_tag << 8;
 }
 

drivers/gpu/drm/nouveau/nvkm/subdev/secboot/acr_r367.c +15 -2

index 866877b88797..978ad0790367 100644
@@ -265,6 +265,19 @@ acr_r367_ls_write_wpr(struct acr_r352 *acr, struct list_head *imgs,
 {
        struct ls_ucode_img *_img;
        u32 pos = 0;
+       u32 max_desc_size = 0;
+       u8 *gdesc;
+
+       list_for_each_entry(_img, imgs, node) {
+               const struct acr_r352_ls_func *ls_func =
+                                           acr->func->ls_func[_img->falcon_id];
+
+               max_desc_size = max(max_desc_size, ls_func->bl_desc_size);
+       }
+
+       gdesc = kmalloc(max_desc_size, GFP_KERNEL);
+       if (!gdesc)
+               return -ENOMEM;
 
        nvkm_kmap(wpr_blob);
 

@@ -272,7 +285,6 @@ acr_r367_ls_write_wpr(struct acr_r352 *acr, struct list_head *imgs,
                struct ls_ucode_img_r367 *img = ls_ucode_img_r367(_img);
                const struct acr_r352_ls_func *ls_func =
                                            acr->func->ls_func[_img->falcon_id];
-               u8 gdesc[ls_func->bl_desc_size];
 
                nvkm_gpuobj_memcpy_to(wpr_blob, pos, &img->wpr_header,
                                      sizeof(img->wpr_header));

@@ -298,6 +310,8 @@ acr_r367_ls_write_wpr(struct acr_r352 *acr, struct list_head *imgs,
 
        nvkm_done(wpr_blob);
 
+       kfree(gdesc);
+
        return 0;
 }
 
--

2.17.0

--
Kees Cook
Pixel Security

In the quest to remove all stack VLA usage from the kernel[1], this allocates the working buffers before starting the writing so it won't abort in the middle. This needs an initial walk of the lists to figure out how large the buffer should be.

[1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com

Signed-off-by Kees Cook <[email protected]>

---
 .../nouveau/nvkm/subdev/secboot/acr_r352.c    | 25 ++++++++++++++++---
 .../nouveau/nvkm/subdev/secboot/acr_r367.c    | 16 +++++++++++-
 2 files changed, 37 insertions(+), 4 deletions(-)

drivers/gpu/drm/nouveau/nvkm/subdev/secboot/acr_r352.c +14 -0

index a721354249ce..d02e183717dc 100644
@@ -414,6 +414,20 @@ acr_r352_ls_write_wpr(struct acr_r352 *acr, struct list_head *imgs,
 {
        struct ls_ucode_img *_img;
        u32 pos = 0;
+       u32 max_desc_size = 0;
+       u8 *gdesc;
+
+       /* Figure out how large we need gdesc to be. */
+       list_for_each_entry(_img, imgs, node) {
+               const struct acr_r352_ls_func *ls_func =
+                                           acr->func->ls_func[_img->falcon_id];
+
+               max_desc_size = max(max_desc_size, ls_func->bl_desc_size);
+       }
+
+       gdesc = kmalloc(max_desc_size, GFP_KERNEL);
+       if (!gdesc)
+               return -ENOMEM;
 
        nvkm_kmap(wpr_blob);
 

drivers/gpu/drm/nouveau/nvkm/subdev/secboot/acr_r352.c +8 -2

                nvkm_gpuobj_memcpy_to(wpr_blob, pos, &img->wpr_header,
                                      sizeof(img->wpr_header));

@@ -447,6 +460,8 @@ acr_r352_ls_write_wpr(struct acr_r352 *acr, struct list_head *imgs,
 
        nvkm_done(wpr_blob);
 
+       kfree(gdesc);
+
        return 0;
 }
 

@@ -771,7 +786,11 @@ acr_r352_load(struct nvkm_acr *_acr, struct nvkm_falcon *falcon,
        struct fw_bl_desc *hsbl_desc;
        void *bl, *blob_data, *hsbl_code, *hsbl_data;
        u32 code_size;
-       u8 bl_desc[bl_desc_size];
+       u8 *bl_desc;
+
+       bl_desc = kzalloc(bl_desc_size, GFP_KERNEL);
+       if (!bl_desc)
+               return -ENOMEM;
 
        /* Find the bootloader descriptor for our blob and copy it */
        if (blob == acr->load_blob) {

@@ -802,7 +821,6 @@ acr_r352_load(struct nvkm_acr *_acr, struct nvkm_falcon *falcon,
                              code_size, hsbl_desc->start_tag, 0, false);
 
        /* Generate the BL header */
-       memset(bl_desc, 0, bl_desc_size);
        acr->func->generate_hs_bl_desc(load_hdr, bl_desc, offset);
 
        /*

@@ -811,6 +829,7 @@ acr_r352_load(struct nvkm_acr *_acr, struct nvkm_falcon *falcon,
        nvkm_falcon_load_dmem(falcon, bl_desc, hsbl_desc->dmem_load_off,
                              bl_desc_size, 0);
 
+       kfree(bl_desc);
        return hsbl_desc->start_tag << 8;
 }
 

drivers/gpu/drm/nouveau/nvkm/subdev/secboot/acr_r367.c +15 -2

index 866877b88797..978ad0790367 100644
@@ -265,6 +265,19 @@ acr_r367_ls_write_wpr(struct acr_r352 *acr, struct list_head *imgs,
 {
        struct ls_ucode_img *_img;
        u32 pos = 0;
+       u32 max_desc_size = 0;
+       u8 *gdesc;
+
+       list_for_each_entry(_img, imgs, node) {
+               const struct acr_r352_ls_func *ls_func =
+                                           acr->func->ls_func[_img->falcon_id];
+
+               max_desc_size = max(max_desc_size, ls_func->bl_desc_size);
+       }
+
+       gdesc = kmalloc(max_desc_size, GFP_KERNEL);
+       if (!gdesc)
+               return -ENOMEM;
 
        nvkm_kmap(wpr_blob);
 

@@ -272,7 +285,6 @@ acr_r367_ls_write_wpr(struct acr_r352 *acr, struct list_head *imgs,
                struct ls_ucode_img_r367 *img = ls_ucode_img_r367(_img);
                const struct acr_r352_ls_func *ls_func =
                                            acr->func->ls_func[_img->falcon_id];
-               u8 gdesc[ls_func->bl_desc_size];
 
                nvkm_gpuobj_memcpy_to(wpr_blob, pos, &img->wpr_header,
                                      sizeof(img->wpr_header));

@@ -298,6 +310,8 @@ acr_r367_ls_write_wpr(struct acr_r352 *acr, struct list_head *imgs,
 
        nvkm_done(wpr_blob);
 
+       kfree(gdesc);
+
        return 0;
 }
 
--

2.17.0

--
Kees Cook
Pixel Security
_______________________________________________
Nouveau mailing list
[email protected]
https://lists.freedesktop.org/mailman/listinfo/nouveau

Quoted 38 lines · Kees Cook

In the quest to remove all stack VLA usage from the kernel[1], this allocates the working buffers before starting the writing so it won't abort in the middle. This needs an initial walk of the lists to figure out how large the buffer should be.

[1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com

Signed-off-by Kees Cook <[email protected]>

---
 .../nouveau/nvkm/subdev/secboot/acr_r352.c    | 25 ++++++++++++++++---
 .../nouveau/nvkm/subdev/secboot/acr_r367.c    | 16 +++++++++++-
 2 files changed, 37 insertions(+), 4 deletions(-)

drivers/gpu/drm/nouveau/nvkm/subdev/secboot/acr_r352.c +14 -0

index a721354249ce..d02e183717dc 100644
@@ -414,6 +414,20 @@ acr_r352_ls_write_wpr(struct acr_r352 *acr, struct list_head *imgs,
 {
        struct ls_ucode_img *_img;
        u32 pos = 0;
+       u32 max_desc_size = 0;
+       u8 *gdesc;
+
+       /* Figure out how large we need gdesc to be. */
+       list_for_each_entry(_img, imgs, node) {
+               const struct acr_r352_ls_func *ls_func =
+                                           acr->func->ls_func[_img->falcon_id];
+
+               max_desc_size = max(max_desc_size, ls_func->bl_desc_size);
+       }
+
+       gdesc = kmalloc(max_desc_size, GFP_KERNEL);
+       if (!gdesc)
+               return -ENOMEM;
 
        nvkm_kmap(wpr_blob);
 

drivers/gpu/drm/nouveau/nvkm/subdev/secboot/acr_r352.c acr_r352_ls_write_wpr(struct acr_r352 *acr, struct list_head *imgs, · line 438

Quoted 6 lines

drivers/gpu/drm/nouveau/nvkm/subdev/secboot/acr_r352.c +0 -1

@@ -421,7 +435,6 @@ acr_r352_ls_write_wpr(struct acr_r352 *acr, struct list_head *imgs,
                struct ls_ucode_img_r352 *img = ls_ucode_img_r352(_img);
                const struct acr_r352_ls_func *ls_func =
                                            acr->func->ls_func[_img->falcon_id];
-               u8 gdesc[ls_func->bl_desc_size];
 

if there are no guarantees that (ls_func->bl_desc_size & 0x4 == 0), then we need to memset a bit more, because 4 bytes at the time are actually copied inside nvkm_gpuobj_memcpy_to later in that code, but the last 4 bytes are only partly memset to 0.

If ls_func->bl_desc_size is always a multiple of 0x4, then it isn't as important, but still better to be fixed. Or maybe nvkm_gpuobj_memcpy_to should do that handling and check if the size is a multiple of 0x4 and otherwise handle that case?

Same is valid for the changes in the r367 file.

Quoted 39 lines · Karol Herbst

Quoted 38 lines · Kees Cook

In the quest to remove all stack VLA usage from the kernel[1], this allocates the working buffers before starting the writing so it won't abort in the middle. This needs an initial walk of the lists to figure out how large the buffer should be.

[1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com

Signed-off-by Kees Cook <[email protected]>

---
 .../nouveau/nvkm/subdev/secboot/acr_r352.c    | 25 ++++++++++++++++---
 .../nouveau/nvkm/subdev/secboot/acr_r367.c    | 16 +++++++++++-
 2 files changed, 37 insertions(+), 4 deletions(-)

drivers/gpu/drm/nouveau/nvkm/subdev/secboot/acr_r352.c +14 -0

index a721354249ce..d02e183717dc 100644
@@ -414,6 +414,20 @@ acr_r352_ls_write_wpr(struct acr_r352 *acr, struct list_head *imgs,
 {
        struct ls_ucode_img *_img;
        u32 pos = 0;
+       u32 max_desc_size = 0;
+       u8 *gdesc;
+
+       /* Figure out how large we need gdesc to be. */
+       list_for_each_entry(_img, imgs, node) {
+               const struct acr_r352_ls_func *ls_func =
+                                           acr->func->ls_func[_img->falcon_id];
+
+               max_desc_size = max(max_desc_size, ls_func->bl_desc_size);
+       }
+
+       gdesc = kmalloc(max_desc_size, GFP_KERNEL);
+       if (!gdesc)
+               return -ENOMEM;
 
        nvkm_kmap(wpr_blob);
 

Quoted 11 lines

drivers/gpu/drm/nouveau/nvkm/subdev/secboot/acr_r352.c acr_r352_ls_write_wpr(struct acr_r352 *acr, struct list_head *imgs, · line 438

Quoted 6 lines

drivers/gpu/drm/nouveau/nvkm/subdev/secboot/acr_r352.c +0 -1

@@ -421,7 +435,6 @@ acr_r352_ls_write_wpr(struct acr_r352 *acr, struct list_head *imgs,
                struct ls_ucode_img_r352 *img = ls_ucode_img_r352(_img);
                const struct acr_r352_ls_func *ls_func =
                                            acr->func->ls_func[_img->falcon_id];
-               u8 gdesc[ls_func->bl_desc_size];
 

if there are no guarantees that (ls_func->bl_desc_size & 0x4 == 0), then we need to memset a bit more, because 4 bytes at the time are actually copied inside nvkm_gpuobj_memcpy_to later in that code, but the last 4 bytes are only partly memset to 0.

I think this is unchanged from the original code, yes? The memset() is always against bl_desc_size; I haven't changed that.

Quoted 6 lines

If ls_func->bl_desc_size is always a multiple of 0x4, then it isn't as important, but still better to be fixed. Or maybe nvkm_gpuobj_memcpy_to should do that handling and check if the size is a multiple of 0x4 and otherwise handle that case?

Same is valid for the changes in the r367 file.

Should I resend with both the allocation and the memset getting rounded up to the next multiple of 4?

-Kees

--
Kees Cook
Pixel Security

Your patch is fine as it is though, because it doesn't add a new issue, it just showed us there is a potential one. We should keep that in mind and see how we want to fix that up. I can imagine that this might cause some issues in some places, maybe it is totally fine.