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clk: meson: pll: Fix by 0 division in __pll_params_to_rate() 

[ Upstream commit d8488a4180 ]

Some meson pll registers can be initialized with 0 as N value, introducing
the following division by 0 when computing rate :

  UBSAN: Undefined behaviour in drivers/clk/meson/clk-pll.c:75:9
  division by zero
  CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.4.0-rc3-608075-g86c9af8630e1-dirty #400
  Call trace:
   dump_backtrace+0x0/0x1c0
   show_stack+0x14/0x20
   dump_stack+0xc4/0x100
   ubsan_epilogue+0x14/0x68
   __ubsan_handle_divrem_overflow+0x98/0xb8
   __pll_params_to_rate+0xdc/0x140
   meson_clk_pll_recalc_rate+0x278/0x3a0
   __clk_register+0x7c8/0xbb0
   devm_clk_hw_register+0x54/0xc0
   meson_eeclkc_probe+0xf4/0x1a0
   platform_drv_probe+0x54/0xd8
   really_probe+0x16c/0x438
   driver_probe_device+0xb0/0xf0
   device_driver_attach+0x94/0xa0
   __driver_attach+0x70/0x108
   bus_for_each_dev+0xd8/0x128
   driver_attach+0x30/0x40
   bus_add_driver+0x1b0/0x2d8
   driver_register+0xbc/0x1d0
   __platform_driver_register+0x78/0x88
   axg_driver_init+0x18/0x20
   do_one_initcall+0xc8/0x24c
   kernel_init_freeable+0x2b0/0x344
   kernel_init+0x10/0x128
   ret_from_fork+0x10/0x18

This checks if N is null before doing the division.

Fixes: 7a29a86943 ("clk: meson: Add support for Meson clock controller")
Reviewed-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Remi Pommarel <repk@triplefau.lt>
[jbrunet@baylibre.com: update the comment in above the fix]
Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
5.4-rM2-2.2.x-imx-squashed
Remi Pommarel 2019-12-15 12:47:05 +01:00 committed by Greg Kroah-Hartman
parent 343fc9a268
commit 4d7f8ca608
1 changed files with 9 additions and 0 deletions
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9
drivers/clk/meson/clk-pll.c
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@ -77,6 +77,15 @@ static unsigned long meson_clk_pll_recalc_rate(struct clk_hw *hw,
unsigned int m, n, frac;
n = meson_parm_read(clk->map, &pll->n);
/*
* On some HW, N is set to zero on init. This value is invalid as
* it would result in a division by zero. The rate can't be
* calculated in this case
*/
if (n == 0)
return 0;
m = meson_parm_read(clk->map, &pll->m);
frac = MESON_PARM_APPLICABLE(&pll->frac) ?