[PATCH 4.4 20/86] ring-buffer: Prevent overflow of size in ring_buffer_resize()

From	Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Newsgroups	linux.kernel
Subject	[PATCH 4.4 20/86] ring-buffer: Prevent overflow of size in ring_buffer_resize()
Date	2016-05-31 00:10 +0200
Message-ID	<rEDxM-1RI-23@gated-at.bofh.it> (permalink)
References	<rECs1-VP-3@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Steven Rostedt (Red Hat) <rostedt@goodmis.org>

commit 59643d1535eb220668692a5359de22545af579f6 upstream.

If the size passed to ring_buffer_resize() is greater than MAX_LONG - BUF_PAGE_SIZE
then the DIV_ROUND_UP() will return zero.

Here's the details:

  # echo 18014398509481980 > /sys/kernel/debug/tracing/buffer_size_kb

tracing_entries_write() processes this and converts kb to bytes.

 18014398509481980 << 10 = 18446744073709547520

and this is passed to ring_buffer_resize() as unsigned long size.

 size = DIV_ROUND_UP(size, BUF_PAGE_SIZE);

Where DIV_ROUND_UP(a, b) is (a + b - 1)/b

BUF_PAGE_SIZE is 4080 and here

 18446744073709547520 + 4080 - 1 = 18446744073709551599

where 18446744073709551599 is still smaller than 2^64

 2^64 - 18446744073709551599 = 17

But now 18446744073709551599 / 4080 = 4521260802379792

and size = size * 4080 = 18446744073709551360

This is checked to make sure its still greater than 2 * 4080,
which it is.

Then we convert to the number of buffer pages needed.

 nr_page = DIV_ROUND_UP(size, BUF_PAGE_SIZE)

but this time size is 18446744073709551360 and

 2^64 - (18446744073709551360 + 4080 - 1) = -3823

Thus it overflows and the resulting number is less than 4080, which makes

  3823 / 4080 = 0

an nr_pages is set to this. As we already checked against the minimum that
nr_pages may be, this causes the logic to fail as well, and we crash the
kernel.

There's no reason to have the two DIV_ROUND_UP() (that's just result of
historical code changes), clean up the code and fix this bug.

Fixes: 83f40318dab00 ("ring-buffer: Make removal of ring buffer pages atomic")
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 kernel/trace/ring_buffer.c |    9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -1666,14 +1666,13 @@ int ring_buffer_resize(struct ring_buffe
 	    !cpumask_test_cpu(cpu_id, buffer->cpumask))
 		return size;
 
-	size = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
-	size *= BUF_PAGE_SIZE;
+	nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
 
 	/* we need a minimum of two pages */
-	if (size < BUF_PAGE_SIZE * 2)
-		size = BUF_PAGE_SIZE * 2;
+	if (nr_pages < 2)
+		nr_pages = 2;
 
-	nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
+	size = nr_pages * BUF_PAGE_SIZE;
 
 	/*
 	 * Don't succeed if resizing is disabled, as a reader might be

Thread

[PATCH 4.4 00/86] 4.4.12-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-30 23:00 +0200
  [PATCH 4.4 83/86] hpfs: implement the show_options method Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-30 23:00 +0200
  [PATCH 4.4 80/86] SIGNAL: Move generic copy_siginfo() to signal.h Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-30 23:00 +0200
  [PATCH 4.4 70/86] serial: samsung: Reorder the sequence of clock control when call s3c24xx_serial_set_termios() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-30 23:00 +0200
  [PATCH 4.4 63/86] tty: vt, return error when con_startup fails Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-30 23:00 +0200
  [PATCH 4.4 54/86] USB: leave LPM alone if possible when binding/unbinding interface drivers Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-30 23:00 +0200
  [PATCH 4.4 75/86] ALSA: hda - Fix headphone noise on Dell XPS 13 9360 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-30 23:00 +0200
  [PATCH 4.4 73/86] mcb: Fixed bar number assignment for the gdd Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-30 23:00 +0200
  [PATCH 4.4 77/86] ALSA: hda - Fix headset mic detection problem for one Dell machine Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-30 23:00 +0200
  [PATCH 4.4 78/86] IB/srp: Fix a debug kernel crash Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-30 23:00 +0200
  [PATCH 4.4 01/86] Btrfs: dont use src fd for printk Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-30 23:10 +0200
  [PATCH 4.4 49/86] USB: serial: option: add more ZTE device ids Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-30 23:10 +0200
  [PATCH 4.4 86/86] kbuild: move -Wunused-const-variable to W=1 warning level Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-30 23:20 +0200
  [PATCH 4.4 55/86] usb: gadget: udc: core: Fix argument of dev_err() in usb_gadget_map_request() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-30 23:50 +0200
  [PATCH 4.4 02/86] perf/x86/intel/pt: Generate PMI in the STOP region as well Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-31 00:00 +0200
  [PATCH 4.4 47/86] USB: serial: io_edgeport: fix memory leaks in probe error path Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-31 00:00 +0200
  [PATCH 4.4 11/86] arm/arm64: KVM: Enforce Break-Before-Make on Stage-2 page tables Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-31 00:00 +0200
  [PATCH 4.4 43/86] USB: serial: mxuport: fix use-after-free in probe error path Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-31 00:00 +0200
  [PATCH 4.4 42/86] mei: bus: call mei_cl_read_start under device lock Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-31 00:00 +0200
  [PATCH 4.4 46/86] USB: serial: io_edgeport: fix memory leaks in attach error path Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-31 00:00 +0200
  [PATCH 4.4 51/86] usb: gadget: f_fs: Fix EFAULT generation for async read operations Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-31 00:00 +0200
  [PATCH 4.4 45/86] USB: serial: quatech2: fix use-after-free in probe error path Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-31 00:00 +0200
  [PATCH 4.4 41/86] mei: amthif: discard not read messages Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-31 00:00 +0200
  [PATCH 4.4 31/86] mmc: mmc: Fix partition switch timeout for some eMMCs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-31 00:10 +0200
  [PATCH 4.4 15/86] fs/cifs: correctly to anonymous authentication for the LANMAN authentication Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-31 00:10 +0200
  [PATCH 4.4 29/86] irqchip/gic-v3: Configure all interrupts as non-secure Group-1 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-31 00:10 +0200
  [PATCH 4.4 06/86] arm64: Fix typo in the pmdp_huge_get_and_clear() definition Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-31 00:10 +0200
  [PATCH 4.4 13/86] remove directory incorrectly tries to set delete on close on non-empty directories Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-31 00:10 +0200
  [PATCH 4.4 32/86] mmc: sdhci-acpi: Remove MMC_CAP_BUS_WIDTH_TEST for Intel controllers Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-31 00:10 +0200
  [PATCH 4.4 19/86] ring-buffer: Use long for nr_pages to avoid overflow failures Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-31 00:10 +0200
  [PATCH 4.4 03/86] perf/core: Fix perf_event_open() vs. execve() race Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-31 00:10 +0200
  [PATCH 4.4 20/86] ring-buffer: Prevent overflow of size in ring_buffer_resize() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-31 00:10 +0200
  [PATCH 4.4 28/86] irqchip/gic: Ensure ordering between read of INTACK and shared data Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-31 00:10 +0200
  [PATCH 4.4 05/86] ext4: iterate over buffer heads correctly in move_extent_per_page() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-31 00:10 +0200
  [PATCH 4.4 12/86] kvm: arm64: Fix EC field in inject_abt64 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-31 00:10 +0200
  [PATCH 4.4 09/86] arm64: Implement pmdp_set_access_flags() for hardware AF/DBM Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-31 00:10 +0200
  [PATCH 4.4 07/86] arm64: Ensure pmd_present() returns false after pmd_mknotpresent() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-31 00:10 +0200
  [PATCH 4.4 36/86] mmc: sdhci-pci: Remove MMC_CAP_BUS_WIDTH_TEST for Intel controllers Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-31 00:10 +0200
  [PATCH 4.4 16/86] fs/cifs: correctly to anonymous authentication for the NTLM(v1) authentication Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-31 00:10 +0200
  [PATCH 4.4 33/86] ACPI / osi: Fix an issue that acpi_osi=!* cannot disable ACPICA internal strings Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-31 00:10 +0200
  [PATCH 4.4 18/86] asix: Fix offset calculation in asix_rx_fixup() causing slow transmissions Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-31 00:10 +0200
  [PATCH 4.4 23/86] crypto: sun4i-ss - Replace spinlock_bh by spin_lock_irq{save|restore} Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-31 00:10 +0200
  [PATCH 4.4 38/86] Bluetooth: vhci: purge unhandled skbs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-31 00:10 +0200
  [PATCH 4.4 27/86] Input: pwm-beeper - fix - scheduling while atomic Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-31 00:10 +0200
  [PATCH 4.4 30/86] can: fix handling of unmodifiable configuration options Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-31 00:10 +0200
  [PATCH 4.4 17/86] fs/cifs: correctly to anonymous authentication for the NTLM(v2) authentication Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-31 00:10 +0200
  [PATCH 4.4 10/86] arm64: cpuinfo: Missing NULL terminator in compat_hwcap_str Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-31 00:10 +0200
  [PATCH 4.4 24/86] clk: qcom: msm8916: Fix crypto clock flags Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-31 00:10 +0200
  [PATCH 4.4 14/86] fs/cifs: correctly to anonymous authentication via NTLMSSP Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-31 00:10 +0200
  [PATCH 4.4 22/86] crypto: talitos - fix ahash algorithms registration Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-31 00:10 +0200
  [PATCH 4.4 08/86] arm64: Implement ptep_set_access_flags() for hardware AF/DBM Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-31 00:10 +0200
  [PATCH 4.4 26/86] mfd: omap-usb-tll: Fix scheduling while atomic BUG Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-05-31 00:10 +0200
  Re: [PATCH 4.4 00/86] 4.4.12-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2016-06-01 16:30 +0200

csiph-web