[PATCH 6.6 140/160] gfs2: Validate i_depth for exhash directories

Greg Kroah-Hartman
2026-04-08T18:27:32Z

From: Andrew Price <anprice@redhat.com>

[ Upstream commit 557c024ca7250bb65ae60f16c02074106c2f197b ]

A fuzzer test introduced corruption that ends up with a depth of 0 in
dir_e_read(), causing an undefined shift by 32 at:

index = hash >> (32 - dip->i_depth);

As calculated in an open-coded way in dir_make_exhash(), the minimum
depth for an exhash directory is ilog2(sdp->sd_hash_ptrs) and 0 is
invalid as sdp->sd_hash_ptrs is fixed as sdp->bsize / 16 at mount time.

So we can avoid the undefined behaviour by checking for depth values
lower than the minimum in gfs2_dinode_in(). Values greater than the
maximum are already being checked for there.

Also switch the calculation in dir_make_exhash() to use ilog2() to
clarify how the depth is calculated.

Tested with the syzkaller repro.c and xfstests '-g quick'.

Reported-by: syzbot+4708579bb230a0582a57@syzkaller.appspotmail.com
Signed-off-by: Andrew Price <anprice@redhat.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Ruohan Lan <ruohanlan@aliyun.com>
Tested-by: Hardik Garg <hargar@linux.microsoft.com>
Tested-by: Ron Economos <re@w6rz.net>
Tested-by: Brett A C Sheffield <bacs@librecast.net>
Tested-by: Shuah Khan <skhan@linuxfoundation.org>
Tested-by: Peter Schneider <pschneider1968@googlemail.com>
Tested-by: Pavel Machek (CIP) <pavel@denx.de>
Tested-by: Florian Fainelli <florian.fainelli@broadcom.com>
Tested-by: Jon Hunter <jonathanh@nvidia.com>
Tested-by: Markus Reichelt <lkt+2023@mareichelt.com>
Tested-by: Ronald Warsow <rwarsow@gmx.de>
Tested-by: Takeshi Ogasawara <takeshi.ogasawara@futuring-girl.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/gfs2/dir.c | 6 ++----
fs/gfs2/glops.c | 6 ++++++
2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/fs/gfs2/dir.c b/fs/gfs2/dir.c
index c252400e59994..c4e9488483d90 100644
--- a/fs/gfs2/dir.c
+++ b/fs/gfs2/dir.c
@@ -60,6 +60,7 @@
#include <linux/crc32.h>
#include <linux/vmalloc.h>
#include <linux/bio.h>
+#include <linux/log2.h>

#include "gfs2.h"
#include "incore.h"
@@ -912,7 +913,6 @@ static int dir_make_exhash(struct inode *inode)
struct qstr args;
struct buffer_head *bh, *dibh;
struct gfs2_leaf *leaf;
- int y;
u32 x;
__be64 *lp;
u64 bn;
@@ -979,9 +979,7 @@ static int dir_make_exhash(struct inode *inode)
i_size_write(inode, sdp->sd_sb.sb_bsize / 2);
gfs2_add_inode_blocks(&dip->i_inode, 1);
dip->i_diskflags |= GFS2_DIF_EXHASH;
-
- for (x = sdp->sd_hash_ptrs, y = -1; x; x >>= 1, y++) ;
- dip->i_depth = y;
+ dip->i_depth = ilog2(sdp->sd_hash_ptrs);

gfs2_dinode_out(dip, dibh->b_data);

diff --git a/fs/gfs2/glops.c b/fs/gfs2/glops.c
index 2ec0b6871ae94..f575cd8ff47c1 100644
--- a/fs/gfs2/glops.c
+++ b/fs/gfs2/glops.c
@@ -11,6 +11,7 @@
#include <linux/bio.h>
#include <linux/posix_acl.h>
#include <linux/security.h>
+#include <linux/log2.h>

#include "gfs2.h"
#include "incore.h"
@@ -466,6 +467,11 @@ static int gfs2_dinode_in(struct gfs2_inode *ip, const void *buf)
gfs2_consist_inode(ip);
return -EIO;
}
+ if ((ip->i_diskflags & GFS2_DIF_EXHASH) &&
+ depth < ilog2(sdp->sd_hash_ptrs)) {
+ gfs2_consist_inode(ip);
+ return -EIO;
+ }
ip->i_depth = (u8)depth;
ip->i_entries = be32_to_cpu(str->di_entries);

--
2.53.0