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Subject[098/156] drm/i915: Avoid NULL deref in get_pages() unwind after error.
2.6.33-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Chris Wilson <chris@chris-wilson.co.uk>

commit 1f2b10131f83f7caa67bf1273cec126b4283015d upstream.

Fixes:
http://bugzilla.kernel.org/show_bug.cgi?id=15527
NULL pointer dereference in i915_gem_object_save_bit_17_swizzle

BUG: unable to handle kernel NULL pointer dereference at (null)
IP: [<f82b5d2b>] i915_gem_object_save_bit_17_swizzle+0x5b/0xc0 [i915]
Call Trace:
[<f82aea55>] ? i915_gem_object_put_pages+0x125/0x150 [i915]
[<f82aeb71>] ? i915_gem_object_get_pages+0xf1/0x110 [i915]
[<f82b0de8>] ? i915_gem_object_bind_to_gtt+0xb8/0x2a0 [i915]
[<c02db74d>] ? drm_mm_get_block_generic+0x4d/0x180
[<f82b11cd>] ? i915_gem_mmap_gtt_ioctl+0x16d/0x240 [i915]
[<f82ae786>] ? i915_gem_madvise_ioctl+0x86/0x120 [i915]

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reported-by: maciej.rutecki@gmail.com
Cc: stable@kernel.org
Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
drivers/gpu/drm/i915/i915_gem.c | 21 ++++++++++++---------
1 file changed, 12 insertions(+), 9 deletions(-)
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1470,9 +1470,6 @@ i915_gem_object_put_pages(struct drm_gem
obj_priv->dirty = 0;

for (i = 0; i < page_count; i++) {
- if (obj_priv->pages[i] == NULL)
- break;
-
if (obj_priv->dirty)
set_page_dirty(obj_priv->pages[i]);

@@ -2228,7 +2225,6 @@ i915_gem_object_get_pages(struct drm_gem
struct address_space *mapping;
struct inode *inode;
struct page *page;
- int ret;

if (obj_priv->pages_refcount++ != 0)
return 0;
@@ -2251,11 +2247,9 @@ i915_gem_object_get_pages(struct drm_gem
mapping_gfp_mask (mapping) |
__GFP_COLD |
gfpmask);
- if (IS_ERR(page)) {
- ret = PTR_ERR(page);
- i915_gem_object_put_pages(obj);
- return ret;
- }
+ if (IS_ERR(page))
+ goto err_pages;
+
obj_priv->pages[i] = page;
}

@@ -2263,6 +2257,15 @@ i915_gem_object_get_pages(struct drm_gem
i915_gem_object_do_bit_17_swizzle(obj);

return 0;
+
+err_pages:
+ while (i--)
+ page_cache_release(obj_priv->pages[i]);
+
+ drm_free_large(obj_priv->pages);
+ obj_priv->pages = NULL;
+ obj_priv->pages_refcount--;
+ return PTR_ERR(page);
}

static void i965_write_fence_reg(struct drm_i915_fence_reg *reg)



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