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authorJason A. Donenfeld <Jason@zx2c4.com>2022-06-01 22:45:33 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2023-02-25 11:25:39 +0100
commit38c5d24d87235f5f047c8d868fc1460544993b8b (patch)
tree2f5999e0422c71365c4cd90ebb43ee969334d6ac
parentafec25854ca7c49b60b02bf47674630f9d7e0377 (diff)
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random: always mix cycle counter in add_latent_entropy()
[ 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>
-rw-r--r--include/linux/random.h6
1 files changed, 3 insertions, 3 deletions
diff --git a/include/linux/random.h b/include/linux/random.h
index bd954ecbef90..51133627ba73 100644
--- a/include/linux/random.h
+++ b/include/linux/random.h
@@ -19,14 +19,14 @@ void add_input_randomness(unsigned int type, unsigned int code,
void add_interrupt_randomness(int irq) __latent_entropy;
void add_hwgenerator_randomness(const void *buf, size_t len, size_t entropy);
-#if defined(LATENT_ENTROPY_PLUGIN) && !defined(__CHECKER__)
static inline void add_latent_entropy(void)
{
+#if defined(LATENT_ENTROPY_PLUGIN) && !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
+}
#if IS_ENABLED(CONFIG_VMGENID)
void add_vmfork_randomness(const void *unique_vm_id, size_t len);