linux-stable.git/kernel/printk, branch v4.19.98

printk: fix integer overflow in setup_log_buf()

2019-12-01T08:16:14+00:00

[ Upstream commit d2130e82e9454304e9b91ba9da551b5989af8c27 ]

The way we calculate logbuf free space percentage overflows signed
integer:

	int free;

	free = __LOG_BUF_LEN - log_next_idx;
	pr_info("early log buf free: %u(%u%%)\n",
		free, (free * 100) / __LOG_BUF_LEN);

We support LOG_BUF_LEN of up to 1<<25 bytes. Since setup_log_buf() is
called during early init, logbuf is mostly empty, so

	__LOG_BUF_LEN - log_next_idx

is close to 1<<25. Thus when we multiply it by 100, we overflow signed
integer value range: 100 is 2^6 + 2^5 + 2^2.

Example, booting with LOG_BUF_LEN 1<<25 and log_buf_len=2G
boot param:

[    0.075317] log_buf_len: -2147483648 bytes
[    0.075319] early log buf free: 33549896(-28%)

Make "free" unsigned integer and use appropriate printk() specifier.

Link: http://lkml.kernel.org/r/20181010113308.9337-1-sergey.senozhatsky@gmail.com
To: Steven Rostedt 
Cc: linux-kernel@vger.kernel.org
Cc: Sergey Senozhatsky 
Signed-off-by: Sergey Senozhatsky 
Signed-off-by: Petr Mladek 
Signed-off-by: Sasha Levin

printk: lock/unlock console only for new logbuf entries

2019-12-01T08:16:13+00:00

[ Upstream commit 3ac37a93fa9217e576bebfd4ba3e80edaaeb2289 ]

Prior to commit 5c2992ee7fd8a29 ("printk: remove console flushing special
cases for partial buffered lines") we would do console_cont_flush()
for each pr_cont() to print cont fragments, so console_unlock() would
actually print data:

	pr_cont();
	 console_lock();
	 console_unlock()
	  console_cont_flush(); // print cont fragment
	...
	pr_cont();
	 console_lock();
	 console_unlock()
	  console_cont_flush(); // print cont fragment

We don't do console_cont_flush() anymore, so when we do pr_cont()
console_unlock() does nothing (unless we flushed the cont buffer):

	pr_cont();
	 console_lock();
	 console_unlock();      // noop
	...
	pr_cont();
	 console_lock();
	 console_unlock();      // noop
	...
	pr_cont();
	  cont_flush();
	    console_lock();
	    console_unlock();   // print data

We also wakeup klogd purposelessly for pr_cont() output - un-flushed
cont buffer is not stored in log_buf; there is nothing to pull.

Thus we can console_lock()/console_unlock()/wake_up_klogd() only when
we know that we log_store()-ed a message and there is something to
print to the consoles/syslog.

Link: http://lkml.kernel.org/r/20181002023836.4487-3-sergey.senozhatsky@gmail.com
To: Steven Rostedt 
Cc: Andrew Morton 
Cc: Dmitriy Vyukov 
Cc: Tetsuo Handa 
Cc: Tejun Heo 
Cc: Peter Zijlstra 
Cc: LKML 
Cc: Sergey Senozhatsky 
Signed-off-by: Sergey Senozhatsky 
Signed-off-by: Petr Mladek 
Signed-off-by: Sasha Levin

printk: Give error on attempt to set log buffer length to over 2G

2019-11-24T07:20:46+00:00

[ Upstream commit e6fe3e5b7d16e8f146a4ae7fe481bc6e97acde1e ]

The current printk() is ready to handle log buffer size up to 2G.
Give an explicit error for users who want to use larger log buffer.

Also fix printk formatting to show the 2G as a positive number.

Link: http://lkml.kernel.org/r/20181008135916.gg4kkmoki5bgtco5@pathway.suse.cz
Cc: rostedt@goodmis.org
Cc: linux-kernel@vger.kernel.org
Suggested-by: Sergey Senozhatsky 
Signed-off-by: He Zhe 
Reviewed-by: Sergey Senozhatsky 
[pmladek: Fixed to the really safe limit 2GB.]
Signed-off-by: Petr Mladek 
Signed-off-by: Sasha Levin

printk: Correct wrong casting

2019-11-24T07:20:24+00:00

[ Upstream commit 51a72ab7372d85c96104e58036f1b49ba11e5d2b ]

log_first_seq and console_seq are 64-bit unsigned integers.
Correct a wrong casting that might cut off the output.

Link: http://lkml.kernel.org/r/1538239553-81805-2-git-send-email-zhe.he@windriver.com
Cc: rostedt@goodmis.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: He Zhe 
[sergey.senozhatsky@gmail.com: More descriptive commit message]
Reviewed-by: Sergey Senozhatsky 
Signed-off-by: Petr Mladek 
Signed-off-by: Sasha Levin

printk: CON_PRINTBUFFER console registration is a bit racy

2019-11-24T07:19:45+00:00

[ Upstream commit 884e370ea88c109a3b982f4eb9ecd82510a3a1fe ]

CON_PRINTBUFFER console registration requires us to do several
preparation steps:
- Rollback console_seq to replay logbuf messages which were already
  seen on other consoles;
- Set exclusive_console flag so console_unlock() will ->write() logbuf
  messages only to the exclusive_console driver.

The way we do it, however, is a bit racy

	logbuf_lock_irqsave(flags);
	console_seq = syslog_seq;
	console_idx = syslog_idx;
	logbuf_unlock_irqrestore(flags);
						<< preemption enabled
						<< irqs enabled
	exclusive_console = newcon;
	console_unlock();

We rollback console_seq under logbuf_lock with IRQs disabled, but
we set exclusive_console with local IRQs enabled and logbuf unlocked.
If the system oops-es or panic-s before we set exclusive_console - and
given that we have IRQs and preemption enabled there is such a
possibility - we will re-play all logbuf messages to every registered
console, which may be a bit annoying and time consuming.

Move exclusive_console assignment to the same IRQs-disabled and
logbuf_lock-protected section where we rollback console_seq.

Link: http://lkml.kernel.org/r/20180928095304.9972-1-sergey.senozhatsky@gmail.com
To: Steven Rostedt 
Cc: Sergey Senozhatsky 
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Sergey Senozhatsky 
Signed-off-by: Petr Mladek 
Signed-off-by: Sasha Levin

printk: Do not miss new messages when replaying the log

2019-11-24T07:19:44+00:00

[ Upstream commit f92b070f2dc89a8ff1a0cc8b608e20abef894c7d ]

The variable "exclusive_console" is used to reply all existing messages
on a newly registered console. It is cleared when all messages are out.

The problem is that new messages might appear in the meantime. These
are then visible only on the exclusive console.

The obvious solution is to clear "exclusive_console" after we replay
all messages that were already proceed before we started the reply.

Reported-by: Sergey Senozhatsky 
Link: http://lkml.kernel.org/r/20180913123406.14378-1-pmladek@suse.com
To: Steven Rostedt 
Cc: Peter Zijlstra 
Cc: Sergey Senozhatsky 
Cc: linux-kernel@vger.kernel.org
Acked-by: Sergey Senozhatsky 
Signed-off-by: Petr Mladek 
Signed-off-by: Sasha Levin

printk: Do not lose last line in kmsg buffer dump

2019-10-05T11:10:01+00:00

commit c9dccacfccc72c32692eedff4a27a4b0833a2afd upstream.

kmsg_dump_get_buffer() is supposed to select all the youngest log
messages which fit into the provided buffer.  It determines the correct
start index by using msg_print_text() with a NULL buffer to calculate
the size of each entry.  However, when performing the actual writes,
msg_print_text() only writes the entry to the buffer if the written len
is lesser than the size of the buffer.  So if the lengths of the
selected youngest log messages happen to precisely fill up the provided
buffer, the last log message is not included.

We don't want to modify msg_print_text() to fill up the buffer and start
returning a length which is equal to the size of the buffer, since
callers of its other users, such as kmsg_dump_get_line(), depend upon
the current behaviour.

Instead, fix kmsg_dump_get_buffer() to compensate for this.

For example, with the following two final prints:

[    6.427502] AAAAAAAAAAAAA
[    6.427769] BBBBBBBB12345

A dump of a 64-byte buffer filled by kmsg_dump_get_buffer(), before this
patch:

 00000000: 3c 30 3e 5b 20 20 20 20 36 2e 35 32 32 31 39 37  <0>[    6.522197
 00000010: 5d 20 41 41 41 41 41 41 41 41 41 41 41 41 41 0a  ] AAAAAAAAAAAAA.
 00000020: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
 00000030: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................

After this patch:

 00000000: 3c 30 3e 5b 20 20 20 20 36 2e 34 35 36 36 37 38  <0>[    6.456678
 00000010: 5d 20 42 42 42 42 42 42 42 42 31 32 33 34 35 0a  ] BBBBBBBB12345.
 00000020: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
 00000030: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................

Link: http://lkml.kernel.org/r/20190711142937.4083-1-vincent.whitchurch@axis.com
Fixes: e2ae715d66bf4bec ("kmsg - kmsg_dump() use iterator to receive log buffer content")
To: rostedt@goodmis.org
Cc: linux-kernel@vger.kernel.org
Cc:  # v3.5+
Signed-off-by: Vincent Whitchurch 
Reviewed-by: Sergey Senozhatsky 
Signed-off-by: Petr Mladek 
Signed-off-by: Greg Kroah-Hartman

printk: Fix panic caused by passing log_buf_len to command line

2018-11-13T19:08:48+00:00

commit 277fcdb2cfee38ccdbe07e705dbd4896ba0c9930 upstream.

log_buf_len_setup does not check input argument before passing it to
simple_strtoull. The argument would be a NULL pointer if "log_buf_len",
without its value, is set in command line and thus causes the following
panic.

PANIC: early exception 0xe3 IP 10:ffffffffaaeacd0d error 0 cr2 0x0
[    0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 4.19.0-rc4-yocto-standard+ #1
[    0.000000] RIP: 0010:_parse_integer_fixup_radix+0xd/0x70
...
[    0.000000] Call Trace:
[    0.000000]  simple_strtoull+0x29/0x70
[    0.000000]  memparse+0x26/0x90
[    0.000000]  log_buf_len_setup+0x17/0x22
[    0.000000]  do_early_param+0x57/0x8e
[    0.000000]  parse_args+0x208/0x320
[    0.000000]  ? rdinit_setup+0x30/0x30
[    0.000000]  parse_early_options+0x29/0x2d
[    0.000000]  ? rdinit_setup+0x30/0x30
[    0.000000]  parse_early_param+0x36/0x4d
[    0.000000]  setup_arch+0x336/0x99e
[    0.000000]  start_kernel+0x6f/0x4ee
[    0.000000]  x86_64_start_reservations+0x24/0x26
[    0.000000]  x86_64_start_kernel+0x6f/0x72
[    0.000000]  secondary_startup_64+0xa4/0xb0

This patch adds a check to prevent the panic.

Link: http://lkml.kernel.org/r/1538239553-81805-1-git-send-email-zhe.he@windriver.com
Cc: stable@vger.kernel.org
Cc: rostedt@goodmis.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: He Zhe 
Reviewed-by: Sergey Senozhatsky 
Signed-off-by: Petr Mladek 
Signed-off-by: Greg Kroah-Hartman

Merge tag 'printk-for-4.19-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk

2018-09-14T05:37:08+00:00

Pull printk fix from Petr Mladek:
 "Revert a commit that caused "quiet", "debug", and "loglevel" early
  parameters to be ignored for early boot messages"

* tag 'printk-for-4.19-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk:
  Revert "printk: make sure to print log on console."

Revert "printk: make sure to print log on console."

2018-09-11T08:04:34+00:00

This reverts commit 375899cddcbb26881b03cb3fbdcfd600e4e67f4a.

The visibility of early messages did not longer take into account
"quiet", "debug", and "loglevel" early parameters.

It would be possible to invalidate and recompute LOG_NOCONS flag
for the affected messages. But it would be hairy.

Instead this patch just reverts the problematic commit. We could
come up with a better solution for the original problem. For example,
we could simplify the logic and just mark messages that should always
be visible or always invisible on the console.

Also this patch reverts the related build fix commit ffaa619af1b06
("printk: Fix warning about unused suppress_message_printing").

Finally, this patch does not put back the unused LOG_NOCONS flag.

Link: http://lkml.kernel.org/r/20180910145747.emvfzv4mzlk5dfqk@pathway.suse.cz
Cc: Thomas Gleixner 
Cc: Ingo Molnar 
Cc: "H . Peter Anvin" 
Cc: x86@kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: Steven Rostedt 
Cc: Maninder Singh 
Reported-by: Hans de Goede 
Acked-by: Hans de Goede 
Acked-by: Sergey Senozhatsky 
Signed-off-by: Petr Mladek