Re: [PATCH] drm/i915: Fix a crash in shmem_pin_map() error handling

[Dan Carpenter]

On Fri, Oct 23, 2020 at 02:19:41PM +0200, Christoph Hellwig wrote:
> > diff --git a/drivers/gpu/drm/i915/gt/shmem_utils.c 
> > b/drivers/gpu/drm/i915/gt/shmem_utils.c
> > index f011ea42487e..7eb542018219 100644
> > --- a/drivers/gpu/drm/i915/gt/shmem_utils.c
> > +++ b/drivers/gpu/drm/i915/gt/shmem_utils.c
> > @@ -52,8 +52,9 @@ struct file *shmem_create_from_object(struct 
> > drm_i915_gem_object *obj)
> >  void *shmem_pin_map(struct file *file)
> >  {
> > struct page **pages;
> > -   size_t n_pages, i;
> > +   size_t n_pages;
> > void *vaddr;
> > +   int i;
> >  
> > n_pages = file->f_mapping->host->i_size >> PAGE_SHIFT;
> > pages = kvmalloc_array(n_pages, sizeof(*pages), GFP_KERNEL);
> 
> This assumes we never have more than INT_MAX worth of pages before
> a failure. 

Doh.  Yeah.  My bad.

regards,
dan carpenter
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[PATCH] drm/i915: Fix a crash in shmem_pin_map() error handling

[Dan Carpenter]

There is a signedness bug in shmem_pin_map() error handling because "i"
is unsigned.  The "while (--i >= 0)" will loop forever until the system
crashes.

Fixes: bfed6708d6c9 ("drm/i915: use vmap in shmem_pin_map")
Signed-off-by: Dan Carpenter 
---
 drivers/gpu/drm/i915/gt/shmem_utils.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gt/shmem_utils.c 
b/drivers/gpu/drm/i915/gt/shmem_utils.c
index f011ea42487e..7eb542018219 100644
--- a/drivers/gpu/drm/i915/gt/shmem_utils.c
+++ b/drivers/gpu/drm/i915/gt/shmem_utils.c
@@ -52,8 +52,9 @@ struct file *shmem_create_from_object(struct 
drm_i915_gem_object *obj)
 void *shmem_pin_map(struct file *file)
 {
struct page **pages;
-   size_t n_pages, i;
+   size_t n_pages;
void *vaddr;
+   int i;
 
n_pages = file->f_mapping->host->i_size >> PAGE_SHIFT;
pages = kvmalloc_array(n_pages, sizeof(*pages), GFP_KERNEL);
-- 
2.28.0

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