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Tue, 13 Dec 2022 02:35:04 -0800 (PST) Received: from MacBook-Pro-6.lan ([2a0d:6fc2:218c:1a00:a0bd:cef2:7a82:b529]) by smtp.gmail.com with ESMTPSA id v15-20020a5d6b0f000000b002366553eca7sm11295813wrw.83.2022.12.13.02.35.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 13 Dec 2022 02:35:04 -0800 (PST) From: david.keisarschm@mail.huji.ac.il To: linux-kernel@vger.kernel.org, Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Vlastimil Babka , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com> Cc: David , aksecurity@gmail.com, ilay.bahat1@gmail.com, linux-mm@kvack.org Subject: [PATCH v2 1/3] Replace invocation of weak PRNG in mm/slab.c Date: Tue, 13 Dec 2022 12:34:57 +0200 Message-Id: <4925f0fe15e9cda5f9d90d75c6e15acdc413ef9e.1670890407.git.david.keisarschm@mail.huji.ac.il> X-Mailer: git-send-email 2.38.0 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 7183720016 X-Stat-Signature: mdny3uchnpkiq6dibf8z9iqzrozgpijd X-HE-Tag: 1670927706-206375 X-HE-Meta: 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 2KjY8XoG lA9mMyXndWo3DzT/knQ+P1Xh6MVxIqqtYhfTSd7y3SdbgIMa/h1bwEbfAgJBYU05W7GLoEevyXNdz8P3d83yf6H2AYMwiu+vtDAq3IXC9VJsAfvLQcJazH45Jsi85RMtjQPENozFB9Sj0sLB3awTzRCx/LBMUlcTj1GJfZpSMba3Qx1gKCJc6isW9A5Trcbr6AziGHjBuWsEZBRTqJciAIajJsw== 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: From: David We changed the invocation of prandom_u32_state to get_random_u32. We also changed the freelist_init_state to struct instead of a union, since the rnd_state is not needed anymore - get_random_u32 maintains its own state. This change it important since it is make the slab allocator randomization stronger. Signed-off-by: David --- mm/slab.c | 20 ++++++++------------ 1 file changed, 8 insertions(+), 12 deletions(-) diff --git a/mm/slab.c b/mm/slab.c index 92d6b1d48..1476104f4 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -2360,20 +2360,17 @@ static void cache_init_objs_debug(struct kmem_cache *cachep, struct slab *slab) #ifdef CONFIG_SLAB_FREELIST_RANDOM /* Hold information during a freelist initialization */ -union freelist_init_state { - struct { - unsigned int pos; - unsigned int *list; - unsigned int count; - }; - struct rnd_state rnd_state; +struct freelist_init_state { + unsigned int pos; + unsigned int *list; + unsigned int count; }; /* * Initialize the state based on the randomization method available. * return true if the pre-computed list is available, false otherwise. */ -static bool freelist_state_initialize(union freelist_init_state *state, +static bool freelist_state_initialize(struct freelist_init_state *state, struct kmem_cache *cachep, unsigned int count) { @@ -2385,7 +2382,6 @@ static bool freelist_state_initialize(union freelist_init_state *state, /* Use a random state if the pre-computed list is not available */ if (!cachep->random_seq) { - prandom_seed_state(&state->rnd_state, rand); ret = false; } else { state->list = cachep->random_seq; @@ -2397,7 +2393,7 @@ static bool freelist_state_initialize(union freelist_init_state *state, } /* Get the next entry on the list and randomize it using a random shift */ -static freelist_idx_t next_random_slot(union freelist_init_state *state) +static freelist_idx_t next_random_slot(struct freelist_init_state *state) { if (state->pos >= state->count) state->pos = 0; @@ -2418,7 +2414,7 @@ static void swap_free_obj(struct slab *slab, unsigned int a, unsigned int b) static bool shuffle_freelist(struct kmem_cache *cachep, struct slab *slab) { unsigned int objfreelist = 0, i, rand, count = cachep->num; - union freelist_init_state state; + struct freelist_init_state state; bool precomputed; if (count < 2) @@ -2447,7 +2443,7 @@ static bool shuffle_freelist(struct kmem_cache *cachep, struct slab *slab) /* Fisher-Yates shuffle */ for (i = count - 1; i > 0; i--) { - rand = prandom_u32_state(&state.rnd_state); + rand = get_random_u32(); rand %= (i + 1); swap_free_obj(slab, i, rand); } -- 2.38.0