On Mon, Dec 23, 2024 at 6:37 PM Prabhakar <prabhakar.csengg@xxxxxxxxx> wrote:
> From: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
>
> Avoid triggering a `refcount_t: addition on 0; use-after-free.` warning
> when registering a module clock with the same MSTOP configuration. The
> issue arises when a module clock is registered but not enabled, resulting
> in a `ref_cnt` of 0. Subsequent calls to `refcount_inc()` on such clocks
> cause the kernel to warn about use-after-free.
>
> [ 0.113529] ------------[ cut here ]------------
> [ 0.113537] refcount_t: addition on 0; use-after-free.
> [ 0.113576] WARNING: CPU: 2 PID: 1 at lib/refcount.c:25 refcount_warn_saturate+0x120/0x144
> [ 0.113602] Modules linked in:
> [ 0.113616] CPU: 2 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.13.0-rc3+ #446
> [ 0.113629] Hardware name: Renesas RZ/V2H EVK Board based on r9a09g057h44 (DT)
> [ 0.113641] pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> [ 0.113652] pc : refcount_warn_saturate+0x120/0x144
> [ 0.113664] lr : refcount_warn_saturate+0x120/0x144
> [ 0.113675] sp : ffff8000818aba90
> [ 0.113682] x29: ffff8000818aba90 x28: ffff0000c0d96450 x27: ffff0000c0d96440
> [ 0.113699] x26: 0000000000000014 x25: 0000000000051000 x24: ffff0000c0ad6480
> [ 0.113714] x23: ffff0000c0d96200 x22: ffff800080fae558 x21: 00000000000001e0
> [ 0.113730] x20: ffff0000c0b11c10 x19: ffff8000815ae6f0 x18: 0000000000000006
> [ 0.113745] x17: ffff800081765368 x16: 0000000000000000 x15: 0765076507720766
> [ 0.113760] x14: ffff8000816a3ea0 x13: 0765076507720766 x12: 072d077207650774
> [ 0.113776] x11: ffff8000816a3ea0 x10: 00000000000000ce x9 : ffff8000816fbea0
> [ 0.113791] x8 : 0000000000017fe8 x7 : 00000000fffff000 x6 : ffff8000816fbea0
> [ 0.113806] x5 : 80000000fffff000 x4 : 0000000000000000 x3 : 0000000000000000
> [ 0.113821] x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff0000c0158000
> [ 0.113837] Call trace:
> [ 0.113845] refcount_warn_saturate+0x120/0x144 (P)
> [ 0.113859] rzv2h_cpg_probe+0x7f8/0xa38
> [ 0.113874] platform_probe+0x68/0xdc
> [ 0.113890] really_probe+0xbc/0x2c0
> [ 0.113901] __driver_probe_device+0x78/0x120
> [ 0.113912] driver_probe_device+0x3c/0x154
> [ 0.113923] __driver_attach+0x90/0x1a0
> [ 0.113933] bus_for_each_dev+0x7c/0xe0
> [ 0.113944] driver_attach+0x24/0x30
> [ 0.113954] bus_add_driver+0xe4/0x208
> [ 0.113965] driver_register+0x68/0x124
> [ 0.113975] __platform_driver_probe+0x54/0xd4
> [ 0.113987] rzv2h_cpg_init+0x24/0x30
> [ 0.113998] do_one_initcall+0x60/0x1d4
> [ 0.114013] kernel_init_freeable+0x214/0x278
> [ 0.114028] kernel_init+0x20/0x140
> [ 0.114041] ret_from_fork+0x10/0x20
> [ 0.114052] ---[ end trace 0000000000000000 ]---
>
> Resolve this by checking the `ref_cnt` value before calling
> `refcount_inc()`. If `ref_cnt` is 0, reset it to 1 using `refcount_set()`.
>
> Fixes: 7bd4cb3d6b7c ("clk: renesas: rzv2h: Add MSTOP support")
> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
> ---
> v1->v2
> - Updated commit description
> - Updated fixes tag commit header
Reviewed-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
