linux-stable.git/kernel/printk.c, branch v3.7.3

printk: fix incorrect length from print_time() when seconds > 99999

2013-01-11T17:18:53+00:00

commit 35dac27cedd14c3b6fcd4ba7bc3c31738cfd1831 upstream.

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 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

printk: Fix scheduling-while-atomic problem in console_cpu_notify()

2012-10-17T01:17:44+00:00

The console_cpu_notify() function runs with interrupts disabled in the
CPU_DYING case.  It therefore cannot block, for example, as will happen
when it calls console_lock().  Therefore, remove the CPU_DYING leg of
the switch statement to avoid this problem.

Signed-off-by: Paul E. McKenney 
Reviewed-by: Srivatsa S. Bhat 
Signed-off-by: Linus Torvalds

printk: Fix calculation of length used to discard records

2012-08-12T18:25:50+00:00

While tracking down a weird buffer overflow issue in a program that
looked to be sane, I started double checking the length returned by
syslog(SYSLOG_ACTION_READ_ALL, ...) to make sure it wasn't overflowing
the buffer.

Sure enough, it was.  I saw this in strace:

  11339 syslog(SYSLOG_ACTION_READ_ALL, "<5>[244017.708129] REISERFS (dev"..., 8192) = 8279

It turns out that the loops that calculate how much space the entries
will take when they're copied don't include the newlines and prefixes
that will be included in the final output since prev flags is passed as
zero.

This patch properly accounts for it and fixes the overflow.

CC: stable@kernel.org
Signed-off-by: Jeff Mahoney 
Signed-off-by: Linus Torvalds

printk: only look for prefix levels in kernel messages

2012-07-31T00:25:14+00:00

vprintk_emit() prefix parsing should only be done for internal kernel
messages.  This allows existing behavior to be kept in all cases.

Signed-off-by: Joe Perches 
Cc: Kay Sievers 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

printk: add generic functions to find KERN_ headers

2012-07-31T00:25:13+00:00

The current form of a KERN_ is "<.>".

Add printk_get_level and printk_skip_level functions to handle these
formats.

These functions centralize tests of KERN_ so a future modification
can change the KERN_ style and shorten the number of bytes consumed
by these headers.

[akpm@linux-foundation.org: fix build error and warning]
Signed-off-by: Joe Perches 
Cc: Kay Sievers 
Cc: Wu Fengguang 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

kmsg: /dev/kmsg - properly return possible copy_from_user() failure

2012-07-31T00:25:13+00:00

Reported-by: Andrew Morton 
Signed-off-by: Kay Sievers 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge tag 'driver-core-3.6-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core

2012-07-26T18:25:33+00:00

Pull driver core changes from Greg Kroah-Hartman:
 "Here's the big driver core pull request for 3.6-rc1.

  Unlike 3.5, this kernel should be a lot tamer, with the printk changes
  now settled down.  All we have here is some extcon driver updates, w1
  driver updates, a few printk cleanups that weren't needed for 3.5, but
  are good to have now, and some other minor fixes/changes in the driver
  core.

  All of these have been in the linux-next releases for a while now.

  Signed-off-by: Greg Kroah-Hartman "

* tag 'driver-core-3.6-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core: (38 commits)
  printk: Export struct log size and member offsets through vmcoreinfo
  Drivers: hv: Change the hex constant to a decimal constant
  driver core: don't trigger uevent after failure
  extcon: MAX77693: Add extcon-max77693 driver to support Maxim MAX77693 MUIC device
  sysfs: fail dentry revalidation after namespace change fix
  sysfs: fail dentry revalidation after namespace change
  extcon: spelling of detach in function doc
  extcon: arizona: Stop microphone detection if we give up on it
  extcon: arizona: Update cable reporting calls and split headset
  PM / Runtime: Do not increment device usage counts before probing
  kmsg - do not flush partial lines when the console is busy
  kmsg - export "continuation record" flag to /dev/kmsg
  kmsg - avoid warning for CONFIG_PRINTK=n compilations
  kmsg - properly print over-long continuation lines
  driver-core: Use kobj_to_dev instead of re-implementing it
  driver-core: Move kobj_to_dev from genhd.h to device.h
  driver core: Move deferred devices to the end of dpm_list before probing
  driver core: move uevent call to driver_register
  driver core: fix shutdown races with probe/remove(v3)
  Extcon: Arizona: Add driver for Wolfson Arizona class devices
  ...

printk: Implement some unlocked kmsg_dump functions

2012-07-21T17:34:00+00:00

If used from KDB, the locked variants are prone to deadlocks (suppose we
got to the debugger w/ the logbuf lock held).

So, we have to implement a few routines that grab no logbuf lock.

Yet we don't need these functions in modules, so we don't export them.

Signed-off-by: Anton Vorontsov 
Signed-off-by: Linus Torvalds

printk: Remove kdb_syslog_data

2012-07-21T17:34:00+00:00

The function is no longer needed, so remove it.

Signed-off-by: Anton Vorontsov 
Signed-off-by: Linus Torvalds

printk: Export struct log size and member offsets through vmcoreinfo

2012-07-20T00:14:18+00:00

There are tools like makedumpfile and vmcore-dmesg which can extract
kernel log buffer from vmcore. Since we introduced structured logging,
that functionality is broken. Now user space tools need to know about
"struct log" and offsets of various fields to be able to parse struct
log data and extract text message or dictonary.

This patch exports some of the fields.

Currently I am not exporting log "level" info as that is a bitfield and
offsetof() bitfields can't be calculated. But if people start asking for
log level info in the output then we probably either need to seprate
out "level" or use bit shift operations for flags and level.

Signed-off-by: Vivek Goyal 
Acked-by: Kay Sievers 
Signed-off-by: Greg Kroah-Hartman