Commit 6cac7866c2741 ("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: 6cac7866c2741 ("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+ --- drivers/hwtracing/intel_th/msu.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-)
diff --git a/drivers/hwtracing/intel_th/msu.c b/drivers/hwtracing/intel_th/msu.c index 6d240dfae9d9..8e48c7458aa3 100644 --- a/drivers/hwtracing/intel_th/msu.c +++ b/drivers/hwtracing/intel_th/msu.c @@ -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;