linux-kernel - [PATCH v2 mm] mm: fix BUG splat with kvmalloc + GFP

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Message-Id: <20220926151650.15293-1-fw@strlen.de>
Date:   Mon, 26 Sep 2022 17:16:50 +0200
From:   Florian Westphal <fw@...len.de>
To:     linux-mm@...ck.org
Cc:     akpm@...ux-foundation.org, mhocko@...e.com, vbabka@...e.cz,
        urezki@...il.com, linux-kernel@...r.kernel.org,
        Florian Westphal <fw@...len.de>,
        Martin Zaharinov <micron10@...il.com>
Subject: [PATCH v2 mm] mm: fix BUG splat with kvmalloc + GFP_ATOMIC

Martin Zaharinov reports BUG with 5.19.10 kernel:
 kernel BUG at mm/vmalloc.c:2437!
 invalid opcode: 0000 [#1] SMP
 CPU: 28 PID: 0 Comm: swapper/28 Tainted: G        W  O      5.19.9 #1
 [..]
 RIP: 0010:__get_vm_area_node+0x120/0x130
  __vmalloc_node_range+0x96/0x1e0
  kvmalloc_node+0x92/0xb0
  bucket_table_alloc.isra.0+0x47/0x140
  rhashtable_try_insert+0x3a4/0x440
  rhashtable_insert_slow+0x1b/0x30
 [..]

bucket_table_alloc uses kvzalloc(GPF_ATOMIC).  If kmalloc fails, this now
falls through to vmalloc and hits code paths that assume GFP_KERNEL.

Reported-by: Martin Zaharinov <micron10@...il.com>
Fixes: a421ef303008 ("mm: allow !GFP_KERNEL allocations for kvmalloc")
Suggested-by: Michal Hocko <mhocko@...e.com>
Link: https://lore.kernel.org/linux-mm/Yy3MS2uhSgjF47dy@pc636/T/#t
Signed-off-by: Florian Westphal <fw@...len.de>
---
 mm/util.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/mm/util.c b/mm/util.c
index c9439c66d8cf..346e40177bc6 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -619,6 +619,10 @@ void *kvmalloc_node(size_t size, gfp_t flags, int node)
 	if (ret || size <= PAGE_SIZE)
 		return ret;

+	/* non-sleeping allocations are not supported by vmalloc */
+	if (!gfpflags_allow_blocking(flags))
+		return NULL;
+
 	/* Don't even allow crazy sizes */
 	if (unlikely(size > INT_MAX)) {
 		WARN_ON_ONCE(!(flags & __GFP_NOWARN));
-- 
2.35.1