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Mon, 31 Jul 2023 15:11:13 -0700 (PDT) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Tue, 1 Aug 2023 00:11:11 +0200 To: Lorenzo Stoakes Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Baoquan He , Uladzislau Rezki , linux-fsdevel@vger.kernel.org, Jiri Olsa , Will Deacon , Mike Galbraith , Mark Rutland , wangkefeng.wang@huawei.com, catalin.marinas@arm.com, ardb@kernel.org, David Hildenbrand , Linux regression tracking , regressions@lists.linux.dev, Matthew Wilcox , Liu Shixin , Jens Axboe , Alexander Viro , stable@vger.kernel.org Subject: Re: [PATCH] fs/proc/kcore: reinstate bounce buffer for KCORE_TEXT regions Message-ID: References: <20230731215021.70911-1-lstoakes@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230731215021.70911-1-lstoakes@gmail.com> X-Rspamd-Queue-Id: AA22F160016 X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: ihzjr5d7j4q13u3rwjywwih8npdhrtci X-HE-Tag: 1690841475-732706 X-HE-Meta: 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 Rk14HKTE 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Jul 31, 2023 at 10:50:21PM +0100, Lorenzo Stoakes wrote: > Some architectures do not populate the entire range categorised by > KCORE_TEXT, so we must ensure that the kernel address we read from is > valid. > > Unfortunately there is no solution currently available to do so with a > purely iterator solution so reinstate the bounce buffer in this instance so > we can use copy_from_kernel_nofault() in order to avoid page faults when > regions are unmapped. > > This change partly reverts commit 2e1c0170771e ("fs/proc/kcore: avoid > bounce buffer for ktext data"), reinstating the bounce buffer, but adapts > the code to continue to use an iterator. > > Fixes: 2e1c0170771e ("fs/proc/kcore: avoid bounce buffer for ktext data") > Reported-by: Jiri Olsa it fixed my issue, thanks Tested-by: Jiri Olsa jirka > Closes: https://lore.kernel.org/all/ZHc2fm+9daF6cgCE@krava > Cc: stable@vger.kernel.org > Signed-off-by: Lorenzo Stoakes > --- > fs/proc/kcore.c | 26 +++++++++++++++++++++++++- > 1 file changed, 25 insertions(+), 1 deletion(-) > > diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c > index 9cb32e1a78a0..3bc689038232 100644 > --- a/fs/proc/kcore.c > +++ b/fs/proc/kcore.c > @@ -309,6 +309,8 @@ static void append_kcore_note(char *notes, size_t *i, const char *name, > > static ssize_t read_kcore_iter(struct kiocb *iocb, struct iov_iter *iter) > { > + struct file *file = iocb->ki_filp; > + char *buf = file->private_data; > loff_t *fpos = &iocb->ki_pos; > size_t phdrs_offset, notes_offset, data_offset; > size_t page_offline_frozen = 1; > @@ -554,11 +556,22 @@ static ssize_t read_kcore_iter(struct kiocb *iocb, struct iov_iter *iter) > fallthrough; > case KCORE_VMEMMAP: > case KCORE_TEXT: > + /* > + * Sadly we must use a bounce buffer here to be able to > + * make use of copy_from_kernel_nofault(), as these > + * memory regions might not always be mapped on all > + * architectures. > + */ > + if (copy_from_kernel_nofault(buf, (void *)start, tsz)) { > + if (iov_iter_zero(tsz, iter) != tsz) { > + ret = -EFAULT; > + goto out; > + } > /* > * We use _copy_to_iter() to bypass usermode hardening > * which would otherwise prevent this operation. > */ > - if (_copy_to_iter((char *)start, tsz, iter) != tsz) { > + } else if (_copy_to_iter(buf, tsz, iter) != tsz) { > ret = -EFAULT; > goto out; > } > @@ -595,6 +608,10 @@ static int open_kcore(struct inode *inode, struct file *filp) > if (ret) > return ret; > > + filp->private_data = kmalloc(PAGE_SIZE, GFP_KERNEL); > + if (!filp->private_data) > + return -ENOMEM; > + > if (kcore_need_update) > kcore_update_ram(); > if (i_size_read(inode) != proc_root_kcore->size) { > @@ -605,9 +622,16 @@ static int open_kcore(struct inode *inode, struct file *filp) > return 0; > } > > +static int release_kcore(struct inode *inode, struct file *file) > +{ > + kfree(file->private_data); > + return 0; > +} > + > static const struct proc_ops kcore_proc_ops = { > .proc_read_iter = read_kcore_iter, > .proc_open = open_kcore, > + .proc_release = release_kcore, > .proc_lseek = default_llseek, > }; > > -- > 2.41.0 >