linux-kernel - [PATCH RFC] drm: omapdrm: do not allow kmalloc to fail

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Message-Id: <1535099243-29679-1-git-send-email-hofrat@osadl.org>
Date:   Fri, 24 Aug 2018 10:27:23 +0200
From:   Nicholas Mc Guire <hofrat@...dl.org>
To:     Tomi Valkeinen <tomi.valkeinen@...com>
Cc:     David Airlie <airlied@...ux.ie>, Andrew F Davis <afd@...com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Nicholas Mc Guire <hofrat@...dl.org>
Subject: [PATCH RFC] drm: omapdrm: do not allow kmalloc to fail

 As this is during init this allocation should not fail and given that the
code is in this state now for 4 years+ this seems to have worked.
kmalloc should be checked though or forced not to fail - Not really sure
but this case seems suitable for __GFP_NOFAIL (relatively small
allocation early in the boot process where it should not fail). The
alternative would probably be a BUG_ON(!new_compat); here.

Issue was introduced by
  commit f2dd36ac9974 ("OMAPDSS: move 'compatible' converter to omapdss driver")

and there is the identical issue in:
  ./drivers/video/fbdev/omap2/omapfb/dss/omapdss-boot-init.c:113:

Pleas let me know if that fix (use of __GFP_NOFAIL) is suitable for this
situation.

Signed-off-by: Nicholas Mc Guire <hofrat@...dl.org>
Fixes: f2dd36ac9974 ("OMAPDSS: move 'compatible' converter to omapdss driver")
---

Issue located with an experimental coccinelle script

Patch was compile tested with: omap2plus_defconfig (implies OMAP2_DSS_INIT=y)

Patch is against 4.18 (localversion-next is next-20180824)


 drivers/gpu/drm/omapdrm/dss/omapdss-boot-init.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/omapdrm/dss/omapdss-boot-init.c b/drivers/gpu/drm/omapdrm/dss/omapdss-boot-init.c
index 3bfb95d..1e07c07 100644
--- a/drivers/gpu/drm/omapdrm/dss/omapdss-boot-init.c
+++ b/drivers/gpu/drm/omapdrm/dss/omapdss-boot-init.c
@@ -110,7 +110,7 @@ static void __init omapdss_omapify_node(struct device_node *node)
 	num_strs = omapdss_count_strings(prop);
 
 	new_len = prop->length + strlen(prefix) * num_strs;
-	new_compat = kmalloc(new_len, GFP_KERNEL);
+	new_compat = kmalloc(new_len, GFP_KERNEL | __GFP_NOFAIL);
 
 	omapdss_prefix_strcpy(new_compat, new_len, prop->value, prop->length);
 
-- 
2.1.4