libmount: (mountinfo) parse empty strings in source
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. Signed-off-by: Alban Crequy <alban@kinvolk.io>
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@ -173,13 +173,36 @@ static int mnt_parse_mountinfo_line(struct libmnt_fs *fs, char *s)
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fs->opt_fields = strndup(s + 1, p - s - 1);
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s = p + 3;
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rc += sscanf(s, UL_SCNsA" " /* (8) FS type */
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UL_SCNsA" " /* (9) source */
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UL_SCNsA, /* (10) fs options (fs specific) */
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end = 0;
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rc += sscanf(s, UL_SCNsA"%n", /* (8) FS type */
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&fstype,
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&src,
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&fs->fs_optstr);
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&end);
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if (rc >= 8 && end > 0)
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s += end;
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if (s[0] == ' ')
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s++;
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/* (9) source can unfortunately be an empty string "" and scanf does
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* not work well with empty string. Test with:
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* $ sudo mount -t tmpfs "" /tmp/bb
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* $ mountpoint /tmp/bb
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* */
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if (s[0] == ' ') {
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src = strdup("");
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s++;
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rc++;
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rc += sscanf(s, UL_SCNsA, /* (10) fs options (fs specific) */
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&fs->fs_optstr);
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} else {
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rc += sscanf(s, UL_SCNsA" " /* (9) source */
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UL_SCNsA, /* (10) fs options (fs specific) */
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&src,
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&fs->fs_optstr);
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}
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if (rc >= 10) {
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size_t sz;
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