linux-kernel - [PATCH RFC] mm: vmalloc: do not allow kzalloc to fail

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Date:   Thu, 20 Dec 2018 21:23:57 +0100
From:   Nicholas Mc Guire <hofrat@...dl.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Chintan Pandya <cpandya@...eaurora.org>,
        Michal Hocko <mhocko@...e.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Arun KS <arunks@...eaurora.org>, Joe Perches <joe@...ches.com>,
        "Luis R. Rodriguez" <mcgrof@...nel.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Nicholas Mc Guire <hofrat@...dl.org>
Subject: [PATCH RFC] mm: vmalloc: do not allow kzalloc to fail

While this is in a very early stage of the system boot and if memory
were exhausted the system has a more serious problem anyway - but still
the kzalloc here seems unsafe. Looking at the history it was previously
switched from alloc_bootmem() to kzalloc() using GFP_NOWAIT flag but
there never seems to have been a check for NULL return. So if this is
expected to never fail should it not be using | __GFP_NOFAIL here ?
Or put differently - what is the rational for GFP_NOWAIT to be safe here ?

Signed-off-by: Nicholas Mc Guire <hofrat@...dl.org>
Fixes 43ebdac42f16 ("vmalloc: use kzalloc() instead of alloc_bootmem()")
---

Problem was found by an experimental coccinelle script

Patch was only compile tested for x86_64_defconfig

Patch is against v4.20-rc7 (localversion-next next-20181220)

 mm/vmalloc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 871e41c..1c118d7 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1258,7 +1258,7 @@ void __init vmalloc_init(void)
 
 	/* Import existing vmlist entries. */
 	for (tmp = vmlist; tmp; tmp = tmp->next) {
-		va = kzalloc(sizeof(struct vmap_area), GFP_NOWAIT);
+		va = kzalloc(sizeof(*va), GFP_NOWAIT | __GFP_NOFAIL);
 		va->flags = VM_VM_AREA;
 		va->va_start = (unsigned long)tmp->addr;
 		va->va_end = va->va_start + tmp->size;
-- 
2.1.4