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Thu, 7 Sep 2023 13:42:20 +0100 Received: from AcuMS.Aculab.com ([::1]) by AcuMS.aculab.com ([::1]) with mapi id 15.00.1497.048; Thu, 7 Sep 2023 13:42:20 +0100 From: David Laight To: 'Vlastimil Babka' , "linux-kernel@vger.kernel.org" , "'linux-mm@kvack.org'" CC: 'Kees Cook' , 'Christoph Lameter' , 'Pekka Enberg' , 'David Rientjes' , 'Joonsoo Kim' , 'Andrew Morton' , 'Eric Dumazet' , "Hyeonggon Yoo" <42.hyeyoo@gmail.com>, Roman Gushchin Subject: Subject: [PATCH v2] slab: kmalloc_size_roundup() must not return 0 for non-zero size Thread-Topic: Subject: [PATCH v2] slab: kmalloc_size_roundup() must not return 0 for non-zero size Thread-Index: Adnhh8rbtLpHk7QBQE+HpPR0NWDZ5g== Date: Thu, 7 Sep 2023 12:42:20 +0000 Message-ID: <4d31a2bf7eb544749023cf491c0eccc8@AcuMS.aculab.com> Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US X-Rspamd-Queue-Id: 3EC2D14001E X-Rspam-User: X-Stat-Signature: cncgkf1jdt3716dh5bw3w4tcpzr41bbf X-Rspamd-Server: rspam03 X-HE-Tag: 1694090546-473933 X-HE-Meta: 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 UXETd5CP k3zluflhcqhMjQ4fTY2Pp+5PZymA7LZZIlwqyIwmLFvzdB2oDIyGoyxirvnZJSPh3iTyGnsLDhtbsfjaj8TE5zycHnQhaFNCcJfzHf5+f4//sk6f0Os8oVvN54z6NT4U2lmRtVzg9gzHcsVN3Dl3lJQX9jCQtSpZ3DjeEGJMwA/s2dTColSQt2MmNjhykZrsIR9Y8VlDaBejxOv2XrUnWOAEvtvvm9+yYAql/EGmATXhX6FUfHBY+uToIINod+XcpaGZIMnsUNuKSazezzri/LM+C214c+mjagK0jxm7k03Cq0vWqxhL6XzCgRRVAk4PIAChnV8yH3Y1ZiIIZQSMP7lDea9xZ6UaWFyPZY/rk+97MkEBVwRHJizskNr9qljEE7drr2j+wgfAahkD93JL4+K9LrL6+0NbzA4AB X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: The typical use of kmalloc_size_roundup() is: ptr = kmalloc(sz = kmalloc_size_roundup(size), ...); if (!ptr) return -ENOMEM. This means it is vitally important that the returned value isn't less than the argument even if the argument is insane. In particular if kmalloc_slab() fails or the value is above (MAX_ULONG - PAGE_SIZE) zero is returned and kmalloc() will return it's single zero-length buffer. Fix by returning the input size on error or if the size exceeds a 'sanity' limit. kmalloc() will then return NULL is the size really is too big. Signed-off-by: David Laight Fixes: 05a940656e1eb ("slab: Introduce kmalloc_size_roundup()") Signed-off-by: David Laight Signed-off-by: Vlastimil Babka Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com> --- v2: - Use KMALLOC_MAX_SIZE for upper limit. (KMALLOC_MAX_SIZE + 1 may give better code on some archs!) - Invert test for overlarge for consistency. - Put a likely() on result of kmalloc_slab(). mm/slab_common.c | 26 +++++++++++++------------- 1 file changed, 13 insertions(+), 13 deletions(-) diff --git a/mm/slab_common.c b/mm/slab_common.c index cd71f9581e67..0fb7c7e19bad 100644 --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -747,22 +747,22 @@ size_t kmalloc_size_roundup(size_t size) { struct kmem_cache *c; - /* Short-circuit the 0 size case. */ - if (unlikely(size == 0)) - return 0; - /* Short-circuit saturated "too-large" case. */ - if (unlikely(size == SIZE_MAX)) - return SIZE_MAX; + if (size && size <= KMALLOC_MAX_CACHE_SIZE) { + /* + * The flags don't matter since size_index is common to all. + * Neither does the caller for just getting ->object_size. + */ + c = kmalloc_slab(size, GFP_KERNEL, 0); + return likely(c) ? c->object_size : size; + } + /* Above the smaller buckets, size is a multiple of page size. */ - if (size > KMALLOC_MAX_CACHE_SIZE) + if (size && size <= KMALLOC_MAX_SIZE) return PAGE_SIZE << get_order(size); - /* - * The flags don't matter since size_index is common to all. - * Neither does the caller for just getting ->object_size. - */ - c = kmalloc_slab(size, GFP_KERNEL, 0); - return c ? c->object_size : 0; + /* Return 'size' for 0 and very large - kmalloc() may fail. */ + return size; + } EXPORT_SYMBOL(kmalloc_size_roundup);