On Fri, Jun 22, 2018 at 01:54:25PM +0200, Alban Crequy wrote: > From: Alban Crequy <alban@xxxxxxxxxx> > > The source of a mount in /proc/self/mountinfo can unfortunately be an > empty string. Before this patch, 'mount' and 'mountpoint' fail as > following: > > $ sudo mount -t tmpfs "" /tmp/bb > $ mount > mount: /proc/self/mountinfo: parse error at line 64 -- ignored > $ mountpoint /tmp/bb > /tmp/bb is not a mountpoint > > This patch fixes the parsing. It is unfortunately more complex because > sscanf() does not handle fields with empty strings easily. > > Other projects have their own parser for mountinfo and have similar > issues. I know of runc and runtime-tools (I'll send a patch for those > two) but there are probably others. The right place is to fix kernel rather than all places where we parse the file in userspace. There is already a pending trivial kernel patch: https://patchwork.kernel.org/patch/10349095/ ... but not sure about the current status of the patch :-( Karel > > Signed-off-by: Alban Crequy <alban@xxxxxxxxxx> > --- > libmount/src/tab_parse.c | 33 ++++++++++++++++++++++++++++----- > 1 file changed, 28 insertions(+), 5 deletions(-) > > diff --git a/libmount/src/tab_parse.c b/libmount/src/tab_parse.c > index 3ed84ebc2..4944d5f8c 100644 > --- a/libmount/src/tab_parse.c > +++ b/libmount/src/tab_parse.c > @@ -173,13 +173,36 @@ static int mnt_parse_mountinfo_line(struct libmnt_fs *fs, char *s) > fs->opt_fields = strndup(s + 1, p - s - 1); > s = p + 3; > > - rc += sscanf(s, UL_SCNsA" " /* (8) FS type */ > - UL_SCNsA" " /* (9) source */ > - UL_SCNsA, /* (10) fs options (fs specific) */ > + end = 0; > + rc += sscanf(s, UL_SCNsA"%n", /* (8) FS type */ > > &fstype, > - &src, > - &fs->fs_optstr); > + &end); > + > + if (rc >= 8 && end > 0) > + s += end; > + if (s[0] == ' ') > + s++; > + > + /* (9) source can unfortunately be an empty string "" and scanf does > + * not work well with empty string. Test with: > + * $ sudo mount -t tmpfs "" /tmp/bb > + * $ mountpoint /tmp/bb > + * */ > + if (s[0] == ' ') { > + src = strdup(""); > + s++; > + rc++; > + rc += sscanf(s, UL_SCNsA, /* (10) fs options (fs specific) */ > + > + &fs->fs_optstr); > + } else { > + rc += sscanf(s, UL_SCNsA" " /* (9) source */ > + UL_SCNsA, /* (10) fs options (fs specific) */ > + > + &src, > + &fs->fs_optstr); > + } > > if (rc >= 10) { > size_t sz; > -- > 2.14.3 > -- Karel Zak <kzak@xxxxxxxxxx> http://karelzak.blogspot.com
