linux-kernel - Re: [PATCH next] mtd: maps: physmap: Fix infinite loop crash in ROM type probing

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Date:   Tue, 6 Nov 2018 22:58:29 +0100
From:   Boris Brezillon <boris.brezillon@...tlin.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Marek Vasut <marek.vasut@...il.com>,
        Richard Weinberger <richard@....at>,
        Linus Walleij <linus.walleij@...aro.org>,
        linux-mtd@...ts.infradead.org, linux-mips@...ux-mips.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH next] mtd: maps: physmap: Fix infinite loop crash in ROM
 type probing

On Tue,  6 Nov 2018 22:44:16 +0100
Geert Uytterhoeven <geert@...ux-m68k.org> wrote:

> On Toshiba RBTX4927, where map_probe is supposed to fail:
> 
>     Creating 2 MTD partitions on "physmap-flash.0":
>     0x000000c00000-0x000001000000 : "boot"
>     0x000000000000-0x000000c00000 : "user"
>     physmap-flash physmap-flash.1: physmap platform flash device: [mem 0x1e000000-0x1effffff]
>     CPU 0 Unable to handle kernel paging request at virtual address 00000000, epc == 80320f40, ra == 80321004
>     ...
>     Call Trace:
>     [<80320f40>] get_mtd_chip_driver+0x30/0x8c
>     [<80321004>] do_map_probe+0x20/0x90
>     [<80328448>] physmap_flash_probe+0x484/0x4ec
> 
> The access to rom_probe_types[] was changed from a sentinel-based loop
> to an infinite loop, causing a crash when reaching the sentinel.

Oops. Do you mind if I fix that in-place (squash your changes in
Ricardo's original commit)?

> 
> Fix this by:
>   - Removing the no longer needed sentinel,
>   - Limiting the number of loop iterations to the actual number of ROM
>     types.
> 
> Fixes: c7afe08496fa463e ("mtd: maps: physmap: Invert logic on if/else branch")
> Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> ---
>  drivers/mtd/maps/physmap-core.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/mtd/maps/physmap-core.c b/drivers/mtd/maps/physmap-core.c
> index 33b77bd9022ce251..e8c3b250d8421edc 100644
> --- a/drivers/mtd/maps/physmap-core.c
> +++ b/drivers/mtd/maps/physmap-core.c
> @@ -396,7 +396,7 @@ static int physmap_flash_of_init(struct platform_device *dev)
>  #endif /* IS_ENABLED(CONFIG_MTD_PHYSMAP_OF) */
>  
>  static const char * const rom_probe_types[] = {
> -	"cfi_probe", "jedec_probe", "qinfo_probe", "map_rom", NULL
> +	"cfi_probe", "jedec_probe", "qinfo_probe", "map_rom",
>  };
>  
>  static const char * const part_probe_types[] = {
> @@ -524,7 +524,7 @@ static int physmap_flash_probe(struct platform_device *dev)
>  		} else {
>  			int j;
>  
> -			for (j = 0; ARRAY_SIZE(rom_probe_types); j++) {
> +			for (j = 0; j < ARRAY_SIZE(rom_probe_types); j++) {
>  				info->mtds[i] = do_map_probe(rom_probe_types[j],
>  							     &info->maps[i]);
>  				if (info->mtds[i])