From: "Jason A. Donenfeld" <Jason@zx2c4.com> stable inclusion from stable-v4.19.274 commit e4935368448ce8097dada35163598e93567f1110 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I6TIG1 CVE: NA Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- [ Upstream commit d7bf7f3b813e3755226bcb5114ad2ac477514ebf ] add_latent_entropy() is called every time a process forks, in kernel_clone(). This in turn calls add_device_randomness() using the latent entropy global state. add_device_randomness() does two things: 2) Mixes into the input pool the latent entropy argument passed; and 1) Mixes in a cycle counter, a sort of measurement of when the event took place, the high precision bits of which are presumably difficult to predict. (2) is impossible without CONFIG_GCC_PLUGIN_LATENT_ENTROPY=y. But (1) is always possible. However, currently CONFIG_GCC_PLUGIN_LATENT_ENTROPY=n disables both (1) and (2), instead of just (2). This commit causes the CONFIG_GCC_PLUGIN_LATENT_ENTROPY=n case to still do (1) by passing NULL (len 0) to add_device_randomness() when add_latent_ entropy() is called. Cc: Dominik Brodowski <linux@dominikbrodowski.net> Cc: PaX Team <pageexec@freemail.hu> Cc: Emese Revfy <re.emese@gmail.com> Fixes: 38addce8b600 ("gcc-plugins: Add latent_entropy plugin") Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> Signed-off-by: Sasha Levin <sashal@kernel.org> Conflicts: include/linux/random.h Signed-off-by: Cui GaoSheng <cuigaosheng1@huawei.com> Reviewed-by: yiyang <yiyang13@huawei.com> Reviewed-by: guozihua <guozihua@huawei.com> Reviewed-by: Wang Weiyang <wangweiyang2@huawei.com> Reviewed-by: Xiu Jianfeng <xiujianfeng@huawei.com> Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com> --- include/linux/random.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/include/linux/random.h b/include/linux/random.h index 37209b3b22ae..d05e70d56d26 100644 --- a/include/linux/random.h +++ b/include/linux/random.h @@ -20,15 +20,15 @@ struct random_ready_callback { extern void add_device_randomness(const void *, unsigned int); -#if defined(CONFIG_GCC_PLUGIN_LATENT_ENTROPY) && !defined(__CHECKER__) static inline void add_latent_entropy(void) { +#if defined(CONFIG_GCC_PLUGIN_LATENT_ENTROPY) && !defined(__CHECKER__) add_device_randomness((const void *)&latent_entropy, sizeof(latent_entropy)); -} #else -static inline void add_latent_entropy(void) {} + add_device_randomness(NULL, 0); #endif +} extern void add_input_randomness(unsigned int type, unsigned int code, unsigned int value) __latent_entropy; -- 2.25.1