According to commit "vfs: parse: deal with zero length string value",
kernel will set the param->string to null pointer in vfs_parse_fs_string()
if fs string has zero length.
Yet the problem is that, gfs2_parse_param() will dereferences the
param->string, without checking whether it is a null pointer, which may
trigger a null-ptr-deref bug.
This patch solves it by adding sanity check on param->string
in gfs2_parse_param().
Reported-by: syzbot+da97a57c5b742d05db51@xxxxxxxxxxxxxxxxxxxxxxxxx
Tested-by: syzbot+da97a57c5b742d05db51@xxxxxxxxxxxxxxxxxxxxxxxxx
Cc: agruenba@xxxxxxxxxx
Cc: cluster-devel@xxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: rpeterso@xxxxxxxxxx
Cc: syzkaller-bugs@xxxxxxxxxxxxxxxx
Signed-off-by: Hawkins Jiawei <yin31149@xxxxxxxxx>
---
fs/gfs2/ops_fstype.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/fs/gfs2/ops_fstype.c b/fs/gfs2/ops_fstype.c
index c0cf1d2d0ef5..934746f18c25 100644
--- a/fs/gfs2/ops_fstype.c
+++ b/fs/gfs2/ops_fstype.c
@@ -1446,12 +1446,18 @@ static int gfs2_parse_param(struct fs_context *fc, struct fs_parameter *param)
switch (o) {
case Opt_lockproto:
+ if (!param->string)
+ goto bad_val;
strscpy(args->ar_lockproto, param->string, GFS2_LOCKNAME_LEN);
break;
case Opt_locktable:
+ if (!param->string)
+ goto bad_val;
strscpy(args->ar_locktable, param->string, GFS2_LOCKNAME_LEN);
break;
case Opt_hostdata:
+ if (!param->string)
+ goto bad_val;
strscpy(args->ar_hostdata, param->string, GFS2_LOCKNAME_LEN);
break;
case Opt_spectator:
@@ -1535,6 +1541,10 @@ static int gfs2_parse_param(struct fs_context *fc, struct fs_parameter *param)
return invalfc(fc, "invalid mount option: %s", param->key);
}
return 0;
+
+bad_val:
+ return invalfc(fc, "Bad value '%s' for mount option '%s'\n",
+ param->string, param->key);
}
static int gfs2_reconfigure(struct fs_context *fc)
--
2.25.1
