lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Mon, 4 May 2020 21:59:03 +0000 From: Luis Chamberlain <mcgrof@...nel.org> To: Kees Cook <keescook@...omium.org>, Greg KH <gregkh@...uxfoundation.org> Cc: Christoph Hellwig <hch@....de>, Iurii Zaikin <yzaikin@...gle.com>, Alexey Dobriyan <adobriyan@...il.com>, linux-mm@...ck.org, linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH] sysctl: Make sure proc handlers can't expose heap memory On Mon, May 04, 2020 at 01:32:07PM -0700, Kees Cook wrote: > On Mon, May 04, 2020 at 07:59:37PM +0000, Luis Chamberlain wrote: > > On Mon, May 04, 2020 at 12:08:55PM -0700, Kees Cook wrote: > > > Just as a precaution, make sure that proc handlers don't accidentally > > > grow "count" beyond the allocated kbuf size. > > > > > > Signed-off-by: Kees Cook <keescook@...omium.org> > > > --- > > > This applies to hch's sysctl cleanup tree... > > > --- > > > fs/proc/proc_sysctl.c | 3 +++ > > > 1 file changed, 3 insertions(+) > > > > > > diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c > > > index 15030784566c..535ab26473af 100644 > > > --- a/fs/proc/proc_sysctl.c > > > +++ b/fs/proc/proc_sysctl.c > > > @@ -546,6 +546,7 @@ static ssize_t proc_sys_call_handler(struct file *filp, void __user *ubuf, > > > struct inode *inode = file_inode(filp); > > > struct ctl_table_header *head = grab_header(inode); > > > struct ctl_table *table = PROC_I(inode)->sysctl_entry; > > > + size_t count_max = count; > > > void *kbuf; > > > ssize_t error; > > > > > > @@ -590,6 +591,8 @@ static ssize_t proc_sys_call_handler(struct file *filp, void __user *ubuf, > > > > > > if (!write) { > > > error = -EFAULT; > > > + if (WARN_ON(count > count_max)) > > > + count = count_max; > > > > That would crash a system with panic-on-warn. I don't think we want that? > > Eh? None of the handlers should be making this mistake currently and > it's not a mistake that can be controlled from userspace. WARN() is > absolutely what's wanted here: report an impossible situation (and > handle it gracefully for the bulk of users that don't have > panic_on_warn set). Alrighty, Greg are you OK with this type of WARN_ON()? You recently expressed concerns over its use due to panic-on-warn on another patch. LUis
Powered by blists - more mailing lists