From 35dac27cedd14c3b6fcd4ba7bc3c31738cfd1831 Mon Sep 17 00:00:00 2001 From: Roland Dreier Date: Fri, 4 Jan 2013 15:35:50 -0800 Subject: printk: fix incorrect length from print_time() when seconds > 99999 print_prefix() passes a NULL buf to print_time() to get the length of the time prefix; when printk times are enabled, the current code just returns the constant 15, which matches the format "[%5lu.%06lu] " used to print the time value. However, this is obviously incorrect when the whole seconds part of the time gets beyond 5 digits (100000 seconds is a bit more than a day of uptime). The simple fix is to use snprintf(NULL, 0, ...) to calculate the actual length of the time prefix. This could be micro-optimized but it seems better to have simpler, more readable code here. The bug leads to the syslog system call miscomputing which messages fit into the userspace buffer. If there are enough messages to fill log_buf_len and some have a timestamp >= 100000, dmesg may fail with: # dmesg klogctl: Bad address When this happens, strace shows that the failure is indeed EFAULT due to the kernel mistakenly accessing past the end of dmesg's buffer, since dmesg asks the kernel how big a buffer it needs, allocates a bit more, and then gets an error when it asks the kernel to fill it: syslog(0xa, 0, 0) = 1048576 mmap(NULL, 1052672, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fa4d25d2000 syslog(0x3, 0x7fa4d25d2010, 0x100008) = -1 EFAULT (Bad address) As far as I can see, the bug has been there as long as print_time(), which comes from commit 084681d14e42 ("printk: flush continuation lines immediately to console") in 3.5-rc5. Signed-off-by: Roland Dreier Signed-off-by: Greg Kroah-Hartman Cc: Joe Perches Cc: Sylvain Munaut Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/printk.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'kernel') diff --git a/kernel/printk.c b/kernel/printk.c index 19c0d7bcf24..357f714ddd4 100644 --- a/kernel/printk.c +++ b/kernel/printk.c @@ -870,10 +870,11 @@ static size_t print_time(u64 ts, char *buf) if (!printk_time) return 0; + rem_nsec = do_div(ts, 1000000000); + if (!buf) - return 15; + return snprintf(NULL, 0, "[%5lu.000000] ", (unsigned long)ts); - rem_nsec = do_div(ts, 1000000000); return sprintf(buf, "[%5lu.%06lu] ", (unsigned long)ts, rem_nsec / 1000); } -- cgit v1.2.3-70-g09d2 From 5ba53ff648e785445a32ba39112ed07e4cf588d0 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Sat, 5 Jan 2013 19:13:13 +0100 Subject: signals: sys_ssetmask() uses uninitialized newmask Commit 77097ae503b1 ("most of set_current_blocked() callers want SIGKILL/SIGSTOP removed from set") removed the initialization of newmask by accident, causing ltp to complain like this: ssetmask01 1 TFAIL : sgetmask() failed: TEST_ERRNO=???(0): Success Restore the proper initialization. Reported-and-tested-by: CAI Qian Signed-off-by: Oleg Nesterov Cc: stable@kernel.org # v3.5+ Signed-off-by: Linus Torvalds --- kernel/signal.c | 1 + 1 file changed, 1 insertion(+) (limited to 'kernel') diff --git a/kernel/signal.c b/kernel/signal.c index 7aaa51d8e5b..9692499c77c 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -3286,6 +3286,7 @@ SYSCALL_DEFINE1(ssetmask, int, newmask) int old = current->blocked.sig[0]; sigset_t newset; + siginitset(&newset, newmask); set_current_blocked(&newset); return old; -- cgit v1.2.3-70-g09d2 From 0c4a842349b27d361f1503f6437df303e1b541c9 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Sat, 5 Jan 2013 19:13:29 +0100 Subject: signals: set_current_blocked() can use __set_current_blocked() Cleanup. And I think we need more cleanups, in particular __set_current_blocked() and sigprocmask() should die. Nobody should ever block SIGKILL or SIGSTOP. - Change set_current_blocked() to use __set_current_blocked() - Change sys_sigprocmask() to use set_current_blocked(), this way it should not worry about SIGKILL/SIGSTOP. Signed-off-by: Oleg Nesterov Signed-off-by: Linus Torvalds --- kernel/signal.c | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-) (limited to 'kernel') diff --git a/kernel/signal.c b/kernel/signal.c index 9692499c77c..372771e948c 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -2528,11 +2528,8 @@ static void __set_task_blocked(struct task_struct *tsk, const sigset_t *newset) */ void set_current_blocked(sigset_t *newset) { - struct task_struct *tsk = current; sigdelsetmask(newset, sigmask(SIGKILL) | sigmask(SIGSTOP)); - spin_lock_irq(&tsk->sighand->siglock); - __set_task_blocked(tsk, newset); - spin_unlock_irq(&tsk->sighand->siglock); + __set_current_blocked(newset); } void __set_current_blocked(const sigset_t *newset) @@ -3204,7 +3201,6 @@ SYSCALL_DEFINE3(sigprocmask, int, how, old_sigset_t __user *, nset, if (nset) { if (copy_from_user(&new_set, nset, sizeof(*nset))) return -EFAULT; - new_set &= ~(sigmask(SIGKILL) | sigmask(SIGSTOP)); new_blocked = current->blocked; @@ -3222,7 +3218,7 @@ SYSCALL_DEFINE3(sigprocmask, int, how, old_sigset_t __user *, nset, return -EINVAL; } - __set_current_blocked(&new_blocked); + set_current_blocked(&new_blocked); } if (oset) { -- cgit v1.2.3-70-g09d2