Messages in this thread | | | From | Miquel Raynal <> | Subject | Re: [PATCH 1/2] mtdchar: prevent integer overflow in a safety check | Date | Thu, 9 Jun 2022 15:10:22 +0200 |
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On Mon, 2022-05-16 at 07:06:00 UTC, =?utf-8?b?TWljaGHFgiBLxJlwaWXFhA==?= wrote: > Commit 6420ac0af95d ("mtdchar: prevent unbounded allocation in MEMWRITE > ioctl") added a safety check to mtdchar_write_ioctl() which attempts to > ensure that the write request sent by user space does not extend beyond > the MTD device's size. However, that check contains an addition of two > struct mtd_write_req fields, 'start' and 'len', both of which are u64 > variables. The result of that addition can overflow, allowing the > safety check to be bypassed. > > The arguably simplest fix - changing the data types of the relevant > struct mtd_write_req fields - is not feasible as it would break user > space. > > Fix by making mtdchar_write_ioctl() truncate the value provided by user > space in the 'len' field of struct mtd_write_req, so that only the lower > 32 bits of that field are used, preventing the overflow. > > While the 'ooblen' field of struct mtd_write_req is not currently used > in any similarly flawed safety check, also truncate it to 32 bits, for > consistency with the 'len' field and with other MTD routines handling > OOB data. > > Update include/uapi/mtd/mtd-abi.h accordingly. > > Suggested-by: Richard Weinberger <richard@nod.at> > Signed-off-by: Michał Kępień <kernel@kempniu.pl>
Applied to https://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux.git mtd/next, thanks.
Miquel
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