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[2003:d0:af0c:d200:8ab2:e79e:9971:853b]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-439452533ecsm18136765e9.0.2025.02.10.05.36.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 10 Feb 2025 05:36:46 -0800 (PST) From: Markus Theil To: linux-kernel@vger.kernel.org Cc: intel-gfx@lists.freedesktop.org, netdev@vger.kernel.org, Jason@zx2c4.com, tytso@mit.edu, Markus Theil Subject: [PATCH] prandom: remove next_pseudo_random32 Date: Mon, 10 Feb 2025 14:35:56 +0100 Message-ID: <20250210133556.66431-1-theil.markus@gmail.com> X-Mailer: git-send-email 2.47.2 MIME-Version: 1.0 X-Mailman-Approved-At: Mon, 10 Feb 2025 15:23:40 +0000 X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" next_pseudo_random32 implements a LCG with known bad statistical properties and is only used in two pieces of testing code. Remove and convert users to the remaining single PRNG interface in prandom/random32. This removes another option of using an insecure PRNG. This is a preliminary patch for further prandom cleanup: - In another upcoming patch, I'd like to add more warnings, that prandom must not be used for cryptographic purposes. - Replace the LFSR113 generator with Xoshiro256++, which is known to have better statistical properties and does not need warmup, when seeded properly. Signed-off-by: Markus Theil --- drivers/gpu/drm/i915/selftests/i915_gem.c | 7 ++++--- drivers/media/test-drivers/vivid/vivid-vid-cap.c | 4 +++- include/linux/prandom.h | 6 ------ 3 files changed, 7 insertions(+), 10 deletions(-) diff --git a/drivers/gpu/drm/i915/selftests/i915_gem.c b/drivers/gpu/drm/i915/selftests/i915_gem.c index 0727492576be..14efa6edd9e6 100644 --- a/drivers/gpu/drm/i915/selftests/i915_gem.c +++ b/drivers/gpu/drm/i915/selftests/i915_gem.c @@ -45,13 +45,15 @@ static void trash_stolen(struct drm_i915_private *i915) struct i915_ggtt *ggtt = to_gt(i915)->ggtt; const u64 slot = ggtt->error_capture.start; const resource_size_t size = resource_size(&i915->dsm.stolen); + struct rnd_state prng; unsigned long page; - u32 prng = 0x12345678; /* XXX: fsck. needs some more thought... */ if (!i915_ggtt_has_aperture(ggtt)) return; + prandom_seed_state(&prng, 0x12345678); + for (page = 0; page < size; page += PAGE_SIZE) { const dma_addr_t dma = i915->dsm.stolen.start + page; u32 __iomem *s; @@ -64,8 +66,7 @@ static void trash_stolen(struct drm_i915_private *i915) s = io_mapping_map_atomic_wc(&ggtt->iomap, slot); for (x = 0; x < PAGE_SIZE / sizeof(u32); x++) { - prng = next_pseudo_random32(prng); - iowrite32(prng, &s[x]); + iowrite32(prandom_u32_state(&prng), &s[x]); } io_mapping_unmap_atomic(s); } diff --git a/drivers/media/test-drivers/vivid/vivid-vid-cap.c b/drivers/media/test-drivers/vivid/vivid-vid-cap.c index b166d90177c6..166372d5f927 100644 --- a/drivers/media/test-drivers/vivid/vivid-vid-cap.c +++ b/drivers/media/test-drivers/vivid/vivid-vid-cap.c @@ -300,8 +300,10 @@ void vivid_update_quality(struct vivid_dev *dev) */ freq_modulus = (dev->tv_freq - 676 /* (43.25-1) * 16 */) % (6 * 16); if (freq_modulus > 2 * 16) { + struct rnd_state prng; + prandom_seed_state(&prng, dev->tv_freq ^ 0x55); tpg_s_quality(&dev->tpg, TPG_QUAL_NOISE, - next_pseudo_random32(dev->tv_freq ^ 0x55) & 0x3f); + prandom_u32_state(&prng) & 0x3f); return; } if (freq_modulus < 12 /*0.75 * 16*/ || freq_modulus > 20 /*1.25 * 16*/) diff --git a/include/linux/prandom.h b/include/linux/prandom.h index f2ed5b72b3d6..ff7dcc3fa105 100644 --- a/include/linux/prandom.h +++ b/include/linux/prandom.h @@ -47,10 +47,4 @@ static inline void prandom_seed_state(struct rnd_state *state, u64 seed) state->s4 = __seed(i, 128U); } -/* Pseudo random number generator from numerical recipes. */ -static inline u32 next_pseudo_random32(u32 seed) -{ - return seed * 1664525 + 1013904223; -} - #endif