Commit 05b686b5 authored Dec 17, 2019 by Alexander Shishkin Committed by Greg Kroah-Hartman Dec 17, 2019

intel_th: msu: Fix window switching without windows



Commit 6cac7866 ("intel_th: msu: Add a sysfs attribute to trigger
window switch") adds a NULL pointer dereference in the case when there are
no windows allocated:

> BUG: kernel NULL pointer dereference, address: 0000000000000000
> #PF: supervisor read access in kernel mode
> #PF: error_code(0x0000) - not-present page
> PGD 0 P4D 0
> Oops: 0000 1 SMP
> CPU: 5 PID: 1110 Comm: bash Not tainted 5.5.0-rc1+ #1
> RIP: 0010:msc_win_switch+0xa/0x80 [intel_th_msu]
> Call Trace:
> ? win_switch_store+0x9b/0xc0 [intel_th_msu]
> dev_attr_store+0x17/0x30
> sysfs_kf_write+0x3e/0x50
> kernfs_fop_write+0xda/0x1b0
> __vfs_write+0x1b/0x40
> vfs_write+0xb9/0x1a0
> ksys_write+0x67/0xe0
> __x64_sys_write+0x1a/0x20
> do_syscall_64+0x57/0x1d0
> entry_SYSCALL_64_after_hwframe+0x44/0xa9

Fix that by disallowing window switching with multiwindow buffers without
windows.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Fixes: 6cac7866 ("intel_th: msu: Add a sysfs attribute to trigger window switch")
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reported-by: Ammy Yi <ammy.yi@intel.com>
Tested-by: Ammy Yi <ammy.yi@intel.com>
Cc: stable@vger.kernel.org # v5.2+
Link: https://lore.kernel.org/r/20191217115527.74383-5-alexander.shishkin@linux.intel.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent ab832e38

drivers/hwtracing/intel_th/msu.c

+9 −5

Original line number	Diff line number	Diff line
		@@ -1676,10 +1676,13 @@ static int intel_th_msc_init(struct msc *msc)
		return 0;
		}

		static void msc_win_switch(struct msc *msc)
		static int msc_win_switch(struct msc *msc)
		{
		struct msc_window *first;

		if (list_empty(&msc->win_list))
		return -EINVAL;

		first = list_first_entry(&msc->win_list, struct msc_window, entry);

		if (msc_is_last_win(msc->cur_win))
		@@ -1691,6 +1694,8 @@ static void msc_win_switch(struct msc *msc)
		msc->base_addr = msc_win_base_dma(msc->cur_win);

		intel_th_trace_switch(msc->thdev);

		return 0;
		}

		/**
		@@ -2025,16 +2030,15 @@ win_switch_store(struct device dev, struct device_attribute attr,
		if (val != 1)
		return -EINVAL;

		ret = -EINVAL;
		mutex_lock(&msc->buf_mutex);
		/*
		* Window switch can only happen in the "multi" mode.
		* If a external buffer is engaged, they have the full
		* control over window switching.
		*/
		if (msc->mode != MSC_MODE_MULTI \|\| msc->mbuf)
		ret = -ENOTSUPP;
		else
		msc_win_switch(msc);
		if (msc->mode == MSC_MODE_MULTI && !msc->mbuf)
		ret = msc_win_switch(msc);
		mutex_unlock(&msc->buf_mutex);

		return ret ? ret : size;

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