From: Linus Torvalds Subject: Re: [PATCH] ext2/super: Fix a possible sleep-in-atomic bug in parse_options Date: Fri, 6 Oct 2017 18:37:11 -0700 Message-ID: References: <1507339246-13067-1-git-send-email-baijiaju1990@163.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Cc: Al Viro , Jan Kara , Sagi Grimberg , james.smart@broadcom.com, "linux-ext4@vger.kernel.org" , linux-fsdevel , Linux Kernel Mailing List To: Jia-Ju Bai Return-path: In-Reply-To: <1507339246-13067-1-git-send-email-baijiaju1990@163.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On Fri, Oct 6, 2017 at 6:20 PM, Jia-Ju Bai wrote: > > To fix it, GFP_KERNEL is replaced with GFP_ATOMIC. > This bug is found by my static analysis tool and my code review. I'm not saying your patch is wrong, but it's a shame that we do that extra allocation in match_number() and match_u64int(), and that we don't have anything that is just size-limited. And there really isn't anything saying that we shouldn't do the same silly thing to match_u64int(). Maybe we don't have any actual users that need it for now, but still.. Oh well. I do wonder if we shouldn't just use something like "skip leading zeroes, copy to size-limited stack location instead" because the input length really *is* limited once you skip leading zeroes (and whatever base marker we have). We might have at most a 64-bit value in octal, so 22 bytes max. But I guess just changing the two GFP_KERNEL's to GFP_ATOMIC is much simpler. Linus