From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 61FAD126BF7; Mon, 22 Jun 2026 17:19:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782148769; cv=none; b=MjAprJv3cBMZ/h6X8MiIGPsDWYWgGONuXTLDL/87YdDVpHaVObKERlAGAH89xuzw2PHRC2m3/86WbDg5sV7MMVyZN4E7e7uHJvw3X3BoAdFu3D6p33NgWaYFMCBmQAOpm8lxByDs7M7Wz/LvuLdDeY67pIDY8us2jL6C8ha3jy4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782148769; c=relaxed/simple; bh=tInr4TBaU4MuA49RED8w5Lk/KBSzygWhk6z0Kus2o1I=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type: Content-Disposition:In-Reply-To; b=No2gtJAfd3vN5b1ehQinoyethYcVluJ1s4lfsskCJPCRqQy3OCR+5IUfw3oHYxGeYx15UKIo+/O+8yMDab0tRW5PVMCfa6XzqSgfB71mqDExz/2W2xxriBX8MSqjbXy9Ir4f9DZ1yGGnBfwxj/e6R7vu1FmnXsF4wdVGdcJS09s= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=HfjTl+l+; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="HfjTl+l+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D02671F000E9; Mon, 22 Jun 2026 17:19:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782148768; bh=4e9haZm8PHCtW0GWvaD9CRzSoYpXU2mtDGKOneISMEY=; h=Date:From:To:Cc:Subject:In-Reply-To; b=HfjTl+l+wp2cJ8Snlpc+RMW8EpQBOdg1abBiQ+XV8IFhkPdALF7sqZ3BcTgDgUe9P Vod35zb8PbMj2mVDOdGAkUYEObnCde5t24jaWwGESmBL6pXtlkSz8Ri3TcR8JYnf/k j1Hc+2ndX/WXGTjquNAGyutBPDKPRTYUWgC/mBfKreaALunOuMuDtJEOU565XcnNDc kpDBEGhqHJzHfolvcUnYrbg6vQ/ub+EIPrmevaYV0I4ciKoQCIvOzUerzjaE0Y8s9p 0GWXElf9lnIUezey/fmciIlt2LHKXhRW+ZPl52g02Gqr2vpyz0nBFGS/sVDLnf+KYH EJUl4xcVaMZZg== Date: Mon, 22 Jun 2026 12:19:26 -0500 From: Bjorn Helgaas To: Deepanshu Kartikey Cc: bhelgaas@google.com, kw@linux.com, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+c7604c9fdd7580cca4e0@syzkaller.appspotmail.com Subject: Re: [PATCH v2] PCI/proc: check user access return values in proc_bus_pci_{read,write}() Message-ID: <20260622171926.GA684276@bhelgaas> Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Sun, Jun 21, 2026 at 01:52:17PM +0530, Deepanshu Kartikey wrote: > On Mon, May 4, 2026 at 7:52 AM Deepanshu Kartikey wrote: > > > > proc_bus_pci_write() ignores the return value of __get_user(). On a > > faulting user pointer the extable fixup zeros the destination, and the > > function writes those zeros to PCI configuration space. > > > > syzbot triggers this with writev()-ing a NULL iov_base to > > /proc/bus/pci/00/03.0 (the virtio-blk controller in the syzkaller VM): > > zero is written to the Command register, clearing Bus Master Enable, > > and the disk stops responding. In-flight journal writes never complete > > and jbd2 hangs in wait_on_buffer() indefinitely: > > > > INFO: task jbd2/sda1-8 blocked in I/O wait for more than 143 seconds. > > __wait_on_buffer fs/buffer.c:123 > > jbd2_journal_commit_transaction+0x388a/0x6870 fs/jbd2/commit.c:837 > > kjournald2 fs/jbd2/journal.c:201 > > > > proc_bus_pci_read() has the symmetric problem with __put_user(): a > > faulting user pointer silently drops config-space data and returns > > success. > > > > Switch both functions to get_user()/put_user(), which combine the > > access_ok() check with the load/store and return -EFAULT on failure. > > The up-front access_ok() can be removed accordingly. On error, jump to > > a common label that releases the runtime-PM reference and returns > > -EFAULT. > > > > Reported-by: syzbot+c7604c9fdd7580cca4e0@syzkaller.appspotmail.com > > Closes: https://syzkaller.appspot.com/bug?extid=c7604c9fdd7580cca4e0 > > Tested-by: syzbot+c7604c9fdd7580cca4e0@syzkaller.appspotmail.com > > Signed-off-by: Deepanshu Kartikey > > --- > > Changes in v2: > > - Use get_user()/put_user() and drop access_ok() (Krzysztof) > > - Rename label to err: per kernel convention (Krzysztof) > > - Simplify error path to release runtime-PM and return -EFAULT (Krzysztof) > > - Apply the same fix to proc_bus_pci_read() (Krzysztof) > > --- > > drivers/pci/proc.c | 44 ++++++++++++++++++++++++++++---------------- > > 1 file changed, 28 insertions(+), 16 deletions(-) > > > > diff --git a/drivers/pci/proc.c b/drivers/pci/proc.c > > index ce36e35681e8..8e624d829840 100644 > > --- a/drivers/pci/proc.c > > +++ b/drivers/pci/proc.c > > @@ -53,15 +53,13 @@ static ssize_t proc_bus_pci_read(struct file *file, char __user *buf, > > nbytes = size - pos; > > cnt = nbytes; > > > > - if (!access_ok(buf, cnt)) > > - return -EINVAL; > > - > > pci_config_pm_runtime_get(dev); > > > > if ((pos & 1) && cnt) { > > unsigned char val; > > pci_user_read_config_byte(dev, pos, &val); > > - __put_user(val, buf); > > + if (put_user(val, buf)) > > + goto err; > > buf++; > > pos++; > > cnt--; > > @@ -70,7 +68,8 @@ static ssize_t proc_bus_pci_read(struct file *file, char __user *buf, > > if ((pos & 3) && cnt > 2) { > > unsigned short val; > > pci_user_read_config_word(dev, pos, &val); > > - __put_user(cpu_to_le16(val), (__le16 __user *) buf); > > + if (put_user(cpu_to_le16(val), (__le16 __user *) buf)) > > + goto err; > > buf += 2; > > pos += 2; > > cnt -= 2; > > @@ -79,7 +78,8 @@ static ssize_t proc_bus_pci_read(struct file *file, char __user *buf, > > while (cnt >= 4) { > > unsigned int val; > > pci_user_read_config_dword(dev, pos, &val); > > - __put_user(cpu_to_le32(val), (__le32 __user *) buf); > > + if (put_user(cpu_to_le32(val), (__le32 __user *) buf)) > > + goto err; > > buf += 4; > > pos += 4; > > cnt -= 4; > > @@ -89,7 +89,8 @@ static ssize_t proc_bus_pci_read(struct file *file, char __user *buf, > > if (cnt >= 2) { > > unsigned short val; > > pci_user_read_config_word(dev, pos, &val); > > - __put_user(cpu_to_le16(val), (__le16 __user *) buf); > > + if (put_user(cpu_to_le16(val), (__le16 __user *) buf)) > > + goto err; > > buf += 2; > > pos += 2; > > cnt -= 2; > > @@ -98,7 +99,8 @@ static ssize_t proc_bus_pci_read(struct file *file, char __user *buf, > > if (cnt) { > > unsigned char val; > > pci_user_read_config_byte(dev, pos, &val); > > - __put_user(val, buf); > > + if (put_user(val, buf)) > > + goto err; > > pos++; > > } > > > > @@ -106,6 +108,10 @@ static ssize_t proc_bus_pci_read(struct file *file, char __user *buf, > > > > *ppos = pos; > > return nbytes; > > + > > +err: > > + pci_config_pm_runtime_put(dev); > > + return -EFAULT; > > } > > > > static ssize_t proc_bus_pci_write(struct file *file, const char __user *buf, > > @@ -129,14 +135,12 @@ static ssize_t proc_bus_pci_write(struct file *file, const char __user *buf, > > nbytes = size - pos; > > cnt = nbytes; > > > > - if (!access_ok(buf, cnt)) > > - return -EINVAL; > > - > > pci_config_pm_runtime_get(dev); > > > > if ((pos & 1) && cnt) { > > unsigned char val; > > - __get_user(val, buf); > > + if (get_user(val, buf)) > > + goto err; > > pci_user_write_config_byte(dev, pos, val); > > buf++; > > pos++; > > @@ -145,7 +149,8 @@ static ssize_t proc_bus_pci_write(struct file *file, const char __user *buf, > > > > if ((pos & 3) && cnt > 2) { > > __le16 val; > > - __get_user(val, (__le16 __user *) buf); > > + if (get_user(val, (__le16 __user *) buf)) > > + goto err; > > pci_user_write_config_word(dev, pos, le16_to_cpu(val)); > > buf += 2; > > pos += 2; > > @@ -154,7 +159,8 @@ static ssize_t proc_bus_pci_write(struct file *file, const char __user *buf, > > > > while (cnt >= 4) { > > __le32 val; > > - __get_user(val, (__le32 __user *) buf); > > + if (get_user(val, (__le32 __user *) buf)) > > + goto err; > > pci_user_write_config_dword(dev, pos, le32_to_cpu(val)); > > buf += 4; > > pos += 4; > > @@ -163,7 +169,8 @@ static ssize_t proc_bus_pci_write(struct file *file, const char __user *buf, > > > > if (cnt >= 2) { > > __le16 val; > > - __get_user(val, (__le16 __user *) buf); > > + if (get_user(val, (__le16 __user *) buf)) > > + goto err; > > pci_user_write_config_word(dev, pos, le16_to_cpu(val)); > > buf += 2; > > pos += 2; > > @@ -172,7 +179,8 @@ static ssize_t proc_bus_pci_write(struct file *file, const char __user *buf, > > > > if (cnt) { > > unsigned char val; > > - __get_user(val, buf); > > + if (get_user(val, buf)) > > + goto err; > > pci_user_write_config_byte(dev, pos, val); > > pos++; > > } > > @@ -182,6 +190,10 @@ static ssize_t proc_bus_pci_write(struct file *file, const char __user *buf, > > *ppos = pos; > > i_size_write(ino, dev->cfg_size); > > return nbytes; > > + > > +err: > > + pci_config_pm_runtime_put(dev); > > + return -EFAULT; > > } > > > > #ifdef HAVE_PCI_MMAP > > -- > > 2.43.0 > > > > Gentle Reminder on this patch. Please let me know the status of this > patch. Thanks for the reminder. We're halfway through the merge window for v7.2, so we'll have to look at this for v7.3 after v7.2-rc1 is tagged.