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Wed, 30 Nov 2022 01:50:57 -0800 (PST) Date: Wed, 30 Nov 2022 18:50:52 +0900 From: Hyeonggon Yoo <42.hyeyoo@gmail.com> To: Feng Tang Cc: Vlastimil Babka , Marco Elver , Andrew Morton , Oliver Glitta , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Roman Gushchin , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 2/2] mm/slub, kunit: Add a test case for kmalloc redzone check Message-ID: References: <20221130085451.3390992-1-feng.tang@intel.com> <20221130085451.3390992-2-feng.tang@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221130085451.3390992-2-feng.tang@intel.com> ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1669801860; a=rsa-sha256; cv=none; b=bcnVp5Aje0f2fvOsOHff2a3pLZVpfifPvoTWwu/CK3aLAtj+py7Vb/NbX7IZQPKmzDfL2l a91ZhycJl0u8wVyZ2kuegMaajOPzAhQmSFa1NtUe9hNPfhBVuhxPlcLj0o4BrI2TwryXkv zxFGzFqqKYXrVmGgttGOhBPzLrKxicQ= ARC-Authentication-Results: i=1; imf22.hostedemail.com; 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spf=pass (imf22.hostedemail.com: domain of 42.hyeyoo@gmail.com designates 209.85.210.169 as permitted sender) smtp.mailfrom=42.hyeyoo@gmail.com; dmarc=pass (policy=none) header.from=gmail.com X-Stat-Signature: 583dycdijhwwi998k6s19c5zaapi7xzq X-HE-Tag: 1669801859-627559 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: On Wed, Nov 30, 2022 at 04:54:51PM +0800, Feng Tang wrote: > kmalloc redzone check for slub has been merged, and it's better to add > a kunit case for it, which is inspired by a real-world case as described > in commit 120ee599b5bf ("staging: octeon-usb: prevent memory corruption"): > > " > octeon-hcd will crash the kernel when SLOB is used. This usually happens > after the 18-byte control transfer when a device descriptor is read. > The DMA engine is always transferring full 32-bit words and if the > transfer is shorter, some random garbage appears after the buffer. > The problem is not visible with SLUB since it rounds up the allocations > to word boundary, and the extra bytes will go undetected. > " > > To avoid interrupting the normal functioning of kmalloc caches, a > kmem_cache mimicing kmalloc cache is created with similar flags, and > kmalloc_trace() is used to really test the orig_size and redzone setup. > > Suggested-by: Vlastimil Babka > Signed-off-by: Feng Tang > --- > Changelog: > > since v2: > * only add SLAB_KMALLOC to SLAB_CACHE_FLAGS and SLAB_FLAGS_PERMITTEDa, > and use new wrapper of cache creation(Vlastimil Babka) > > since v1: > * create a new cache mimicing kmalloc cache, reduce dependency > over global slub_debug setting (Vlastimil Babka) > > lib/slub_kunit.c | 22 ++++++++++++++++++++++ > mm/slab.h | 4 +++- > 2 files changed, 25 insertions(+), 1 deletion(-) > > diff --git a/lib/slub_kunit.c b/lib/slub_kunit.c > index 5b0c8e7eb6dc..ff24879e3afe 100644 > --- a/lib/slub_kunit.c > +++ b/lib/slub_kunit.c > @@ -135,6 +135,27 @@ static void test_clobber_redzone_free(struct kunit *test) > kmem_cache_destroy(s); > } > > +static void test_kmalloc_redzone_access(struct kunit *test) > +{ > + struct kmem_cache *s = test_kmem_cache_create("TestSlub_RZ_kmalloc", 32, > + SLAB_KMALLOC|SLAB_STORE_USER|SLAB_RED_ZONE); > + u8 *p = kmalloc_trace(s, GFP_KERNEL, 18); > + > + kasan_disable_current(); > + > + /* Suppress the -Warray-bounds warning */ > + OPTIMIZER_HIDE_VAR(p); > + p[18] = 0xab; > + p[19] = 0xab; > + > + kmem_cache_free(s, p); > + validate_slab_cache(s); > + KUNIT_EXPECT_EQ(test, 2, slab_errors); > + > + kasan_enable_current(); > + kmem_cache_destroy(s); > +} > + > static int test_init(struct kunit *test) > { > slab_errors = 0; > @@ -154,6 +175,7 @@ static struct kunit_case test_cases[] = { > #endif > > KUNIT_CASE(test_clobber_redzone_free), > + KUNIT_CASE(test_kmalloc_redzone_access), > {} > }; > > diff --git a/mm/slab.h b/mm/slab.h > index c71590f3a22b..7cc432969945 100644 > --- a/mm/slab.h > +++ b/mm/slab.h > @@ -344,7 +344,8 @@ static inline slab_flags_t kmem_cache_flags(unsigned int object_size, > SLAB_ACCOUNT) > #elif defined(CONFIG_SLUB) > #define SLAB_CACHE_FLAGS (SLAB_NOLEAKTRACE | SLAB_RECLAIM_ACCOUNT | \ > - SLAB_TEMPORARY | SLAB_ACCOUNT | SLAB_NO_USER_FLAGS) > + SLAB_TEMPORARY | SLAB_ACCOUNT | \ > + SLAB_NO_USER_FLAGS | SLAB_KMALLOC) > #else > #define SLAB_CACHE_FLAGS (SLAB_NOLEAKTRACE) > #endif > @@ -364,6 +365,7 @@ static inline slab_flags_t kmem_cache_flags(unsigned int object_size, > SLAB_RECLAIM_ACCOUNT | \ > SLAB_TEMPORARY | \ > SLAB_ACCOUNT | \ > + SLAB_KMALLOC | \ > SLAB_NO_USER_FLAGS) > > bool __kmem_cache_empty(struct kmem_cache *); > -- > 2.34.1 > Looks good to me. Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com> -- Thanks, Hyeonggon