Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752191Ab3HUGBe (ORCPT ); Wed, 21 Aug 2013 02:01:34 -0400 Received: from mail-oa0-f52.google.com ([209.85.219.52]:41763 "EHLO mail-oa0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752068Ab3HUGBd (ORCPT ); Wed, 21 Aug 2013 02:01:33 -0400 MIME-Version: 1.0 X-Google-Sender-Delegation: getarunks@gmail.com In-Reply-To: <20130820140447.GL27005@ZenIV.linux.org.uk> References: <20130820055153.GH27005@ZenIV.linux.org.uk> <20130820073622.GK27005@ZenIV.linux.org.uk> <20130820140447.GL27005@ZenIV.linux.org.uk> Date: Wed, 21 Aug 2013 11:31:32 +0530 X-Google-Sender-Auth: ptFKOEQEIt1fQM6gqIC_gXX3j7s Message-ID: Subject: Re: [PATCH v1] seq_file: Fix overflow condition in seq_commit From: Arun KS To: Al Viro Cc: Andrew Morton , Matthew Wilcox , Bruce Fields , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, vinayak menon , Nagachandra P , Vikram MP Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5180 Lines: 145 Hi Al Viro, On Tue, Aug 20, 2013 at 7:34 PM, Al Viro wrote: > On Tue, Aug 20, 2013 at 08:36:22AM +0100, Al Viro wrote: > >> Aha. _That_ is a bug, all right - dynamic_dname() is simply not suitable >> for that kind of uses. ashmem.c is certainly abusing shmem_file_setup(); >> feeding that kind of mess as dentry name is a Bad Idea(tm). Anyway, >> I'd suggest this for a fix: >> >> va_list args; >> size_t sz; >> va_start(args, fmt); >> sz = vsnprintf(NULL, 0, fmt, args) + 1; >> va_end(args); >> if (sz > buflen) >> return ERR_PTR(-ENAMETOOLONG); >> va_start(args, fmt); >> buffer += buflen - sz; >> vsprintf(buffer, fmt, args); >> va_end(args); >> return buffer; >> >> Either right in dynamic_dname(), or as possibly_fucking_long_dname(), >> to be used by shmem.c... > > Actually, looking at the users of dynamic_dname()... Most of them are > fine with dynamic_dname() as it is, with 2 possible exceptions: > hugetlb_dname() and shmem_dname(). Both are using "/%s (deleted)", > dentry->d_name.name as format... So the solution above may very > well be an overkill; something like > > char *simple_dname(struct dentry *dentry, char *buffer, int buflen) > { > char *end = buffer + buflen; > /* these dentries are never renamed, so d_lock is not needed */ > if (prepend(&end, &buflen, " (deleted)", 11) || > prepend_name(&end, &buflen, &dentry->d_name) || > prepend(&end, &buflen, "/", 1)) > end = ERR_PTR(-ENAMETOOLONG); > return end; > } > > will do for those two. Care to test the diff below? Patch works fine. Tested-by: Arun KS Thanks, Arun > > cope with potentially long ->d_dname() output for shmem/hugetlb > > dynamic_dname() is both too much and too little for those - the > output may be well in excess of 64 bytes dynamic_dname() assumes > to be enough (thanks to ashmem feeding really long names to > shmem_file_setup()) and vsnprintf() is an overkill for those > guys. > > Signed-off-by: Al Viro > --- > diff --git a/fs/dcache.c b/fs/dcache.c > index 87bdb53..83cfb83 100644 > --- a/fs/dcache.c > +++ b/fs/dcache.c > @@ -2724,6 +2724,17 @@ char *dynamic_dname(struct dentry *dentry, char *buffer, int buflen, > return memcpy(buffer, temp, sz); > } > > +char *simple_dname(struct dentry *dentry, char *buffer, int buflen) > +{ > + char *end = buffer + buflen; > + /* these dentries are never renamed, so d_lock is not needed */ > + if (prepend(&end, &buflen, " (deleted)", 11) || > + prepend_name(&end, &buflen, &dentry->d_name) || > + prepend(&end, &buflen, "/", 1)) > + end = ERR_PTR(-ENAMETOOLONG); > + return end; > +} > + > /* > * Write full pathname from the root of the filesystem into the buffer. > */ > diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c > index a3f868a..4e5f332 100644 > --- a/fs/hugetlbfs/inode.c > +++ b/fs/hugetlbfs/inode.c > @@ -916,14 +916,8 @@ static int get_hstate_idx(int page_size_log) > return h - hstates; > } > > -static char *hugetlb_dname(struct dentry *dentry, char *buffer, int buflen) > -{ > - return dynamic_dname(dentry, buffer, buflen, "/%s (deleted)", > - dentry->d_name.name); > -} > - > static struct dentry_operations anon_ops = { > - .d_dname = hugetlb_dname > + .d_dname = simple_dname > }; > > /* > diff --git a/include/linux/dcache.h b/include/linux/dcache.h > index b90337c..4a12532 100644 > --- a/include/linux/dcache.h > +++ b/include/linux/dcache.h > @@ -336,6 +336,7 @@ extern int d_validate(struct dentry *, struct dentry *); > * helper function for dentry_operations.d_dname() members > */ > extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...); > +extern char *simple_dname(struct dentry *, char *, int); > > extern char *__d_path(const struct path *, const struct path *, char *, int); > extern char *d_absolute_path(const struct path *, char *, int); > diff --git a/mm/shmem.c b/mm/shmem.c > index 8335dbd..e43dc55 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -2909,14 +2909,8 @@ EXPORT_SYMBOL_GPL(shmem_truncate_range); > > /* common code */ > > -static char *shmem_dname(struct dentry *dentry, char *buffer, int buflen) > -{ > - return dynamic_dname(dentry, buffer, buflen, "/%s (deleted)", > - dentry->d_name.name); > -} > - > static struct dentry_operations anon_ops = { > - .d_dname = shmem_dname > + .d_dname = simple_dname > }; > > /** > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/