Re: [PATCH v3] misc: fastrpc: Fix incorrect DMA mapping unmap request

[Ekansh Gupta]

On 8/2/2023 7:13 PM, Srinivas Kandagatla wrote:
> On 02/08/2023 06:10, Ekansh Gupta wrote:
> > Scatterlist table is obtained during map create request and the same
> > table is used for DMA mapping unmap. In case there is any failure
> > while getting the sg_table, ERR_PTR is returned instead of sg_table.
> >
> > When the map is getting freed, there is only a non-NULL check of
> > sg_table which will also be true in case failure was returned instead
> > of sg_table. This would result in improper unmap request. Add proper
> > check before setting map table to avoid bad unmap request.
> >
> > Fixes: c68cfb718c8f ("misc: fastrpc: Add support for context Invoke 
> > method")
> > Cc: stable <stable@xxxxxxxxxx>
> > Signed-off-by: Ekansh Gupta <quic_ekangupt@xxxxxxxxxxx>
> > ---
> > Changes in v2:
> >    - Added fixes information to commit text
> > Changes in v3:
> >    - Set map->table only if attachment for successful
> >
> >   drivers/misc/fastrpc.c | 8 +++++---
> >   1 file changed, 5 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
> > index 9666d28..de7c812 100644
> > --- a/drivers/misc/fastrpc.c
> > +++ b/drivers/misc/fastrpc.c
> > @@ -756,6 +756,7 @@ static int fastrpc_map_create(struct fastrpc_user 
> > *fl, int fd,
> >   {
> >       struct fastrpc_session_ctx *sess = fl->sctx;
> >       struct fastrpc_map *map = NULL;
> > +    struct sg_table *table;
> >       int err = 0;
> >       if (!fastrpc_map_lookup(fl, fd, ppmap, true))
> > @@ -783,11 +784,12 @@ static int fastrpc_map_create(struct 
> > fastrpc_user *fl, int fd,
> >           goto attach_err;
> >       }
> > -    map->table = dma_buf_map_attachment_unlocked(map->attach, 
> > DMA_BIDIRECTIONAL);
> > -    if (IS_ERR(map->table)) {
> > -        err = PTR_ERR(map->table);
> > +    table = dma_buf_map_attachment(map->attach, DMA_BIDIRECTIONAL);
>
> Any reason why dma_buf_map_attachment_unlocked changed to 
> dma_buf_map_attachment?
This is a mistake from my end. My local workspace had older version due 
to which the function also got reverted. I will fix this in new patch. 
Apologies for the confusion.
> --srini
> > +    if (IS_ERR(table)) {
> > +        err = PTR_ERR(table);
> >           goto map_err;
> >       }
> > +    map->table = table;
> >       if (attr & FASTRPC_ATTR_SECUREMAP) {
> >           map->phys = sg_phys(map->table->sgl);