From e33ba5fa7afce1a9f159704121d4e4d110df8185 Mon Sep 17 00:00:00 2001 From: Theodore Ts'o Date: Sun, 15 Jun 2014 21:04:32 -0400 Subject: random: fix nasty entropy accounting bug Commit 0fb7a01af5b0 "random: simplify accounting code", introduced in v3.15, has a very nasty accounting problem when the entropy pool has has fewer bytes of entropy than the number of requested reserved bytes. In that case, "have_bytes - reserved" goes negative, and since size_t is unsigned, the expression: ibytes = min_t(size_t, ibytes, have_bytes - reserved); ... does not do the right thing. This is rather bad, because it defeats the catastrophic reseeding feature in the xfer_secondary_pool() path. It also can cause the "BUG: spinlock trylock failure on UP" for some kernel configurations when prandom_reseed() calls get_random_bytes() in the early init, since when the entropy count gets corrupted, credit_entropy_bits() erroneously believes that the nonblocking pool has been fully initialized (when in fact it is not), and so it calls prandom_reseed(true) recursively leading to the spinlock BUG. The logic is *not* the same it was originally, but in the cases where it matters, the behavior is the same, and the resulting code is hopefully easier to read and understand. Fixes: 0fb7a01af5b0 "random: simplify accounting code" Signed-off-by: Theodore Ts'o Cc: Greg Price Cc: stable@vger.kernel.org #v3.15 --- drivers/char/random.c | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-) (limited to 'drivers/char') diff --git a/drivers/char/random.c b/drivers/char/random.c index 102c50d38902..2b6e4cd8de8e 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -979,7 +979,6 @@ static void push_to_pool(struct work_struct *work) static size_t account(struct entropy_store *r, size_t nbytes, int min, int reserved) { - int have_bytes; int entropy_count, orig; size_t ibytes; @@ -988,17 +987,19 @@ static size_t account(struct entropy_store *r, size_t nbytes, int min, /* Can we pull enough? */ retry: entropy_count = orig = ACCESS_ONCE(r->entropy_count); - have_bytes = entropy_count >> (ENTROPY_SHIFT + 3); ibytes = nbytes; /* If limited, never pull more than available */ - if (r->limit) - ibytes = min_t(size_t, ibytes, have_bytes - reserved); + if (r->limit) { + int have_bytes = entropy_count >> (ENTROPY_SHIFT + 3); + + if ((have_bytes -= reserved) < 0) + have_bytes = 0; + ibytes = min_t(size_t, ibytes, have_bytes); + } if (ibytes < min) ibytes = 0; - if (have_bytes >= ibytes + reserved) - entropy_count -= ibytes << (ENTROPY_SHIFT + 3); - else - entropy_count = reserved << (ENTROPY_SHIFT + 3); + if ((entropy_count -= ibytes << (ENTROPY_SHIFT + 3)) < 0) + entropy_count = 0; if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig) goto retry; -- cgit v1.2.3-58-ga151 From 6d827fbcc370ca259a2905309f64161ab7b10596 Mon Sep 17 00:00:00 2001 From: Guenter Roeck Date: Sat, 21 Jun 2014 08:08:08 -0700 Subject: i8k: Fix non-SMP operation Commit f36fdb9f0266 (i8k: Force SMM to run on CPU 0) adds support for multi-core CPUs to the driver. Unfortunately, that causes it to fail loading if compiled without SMP support, at least on 32 bit kernels. Kernel log shows "i8k: unable to get SMM Dell signature", and function i8k_smm is found to return -EINVAL. Testing revealed that the culprit is the missing return value check of set_cpus_allowed_ptr. Fixes: f36fdb9f0266 (i8k: Force SMM to run on CPU 0) Reported-by: Jim Bos Tested-by: Jim Bos Cc: stable@vger.kernel.org # 3.14+ Signed-off-by: Guenter Roeck Cc: Andreas Mohr Signed-off-by: Greg Kroah-Hartman --- drivers/char/i8k.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'drivers/char') diff --git a/drivers/char/i8k.c b/drivers/char/i8k.c index d915707d2ba1..93dcad0c1cbe 100644 --- a/drivers/char/i8k.c +++ b/drivers/char/i8k.c @@ -138,7 +138,9 @@ static int i8k_smm(struct smm_regs *regs) if (!alloc_cpumask_var(&old_mask, GFP_KERNEL)) return -ENOMEM; cpumask_copy(old_mask, ¤t->cpus_allowed); - set_cpus_allowed_ptr(current, cpumask_of(0)); + rc = set_cpus_allowed_ptr(current, cpumask_of(0)); + if (rc) + goto out; if (smp_processor_id() != 0) { rc = -EBUSY; goto out; -- cgit v1.2.3-58-ga151