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([2405:201:682f:389d:4391:3576:53a6:e191]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-82b0409c681sm17104789b3a.37.2026.03.24.23.05.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 24 Mar 2026 23:05:13 -0700 (PDT) From: Deepanshu Kartikey To: agruenba@redhat.com Cc: gfs2@lists.linux.dev, linux-kernel@vger.kernel.org, Deepanshu Kartikey , syzbot+b441db1854c360b83221@syzkaller.appspotmail.com Subject: [PATCH] gfs2: fix duplicate kmem_cache name on concurrent mounts Date: Wed, 25 Mar 2026 11:35:06 +0530 Message-ID: <20260325060506.4868-1-kartikey406@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" When gfs2_fill_super() creates the per-filesystem bufdata cache, it uses sd_fsname as part of the cache name: sdp->sd_bufdata =3D kmem_cache_create("gfs2-bufdata/", ...); At this point sd_fsname is set from sd_table_name (e.g. "syz:syz"), which is the same for all concurrent mounts of the same device. The unique suffix (.s for spectator, .N for journal ID) is only added to sd_fsname AFTER wait_on_journal() completes, since the journal ID is assigned by the locking subsystem during mount. With multiple concurrent mounts of the same device (as triggered by syzkaller with procs:5), multiple calls to gfs2_fill_super() all try to create a cache named "gfs2-bufdata/syz:syz" before any of them reaches the point where sd_fsname becomes unique, triggering: kmem_cache of name 'gfs2-bufdata/syz:syz' already exists WARNING: mm/slab_common.c:112 Fix this by moving the bufdata cache creation to after wait_on_journal() completes and sd_fsname has been updated with its unique suffix. Also move the fail_bufdata cleanup label accordingly in the error unwind path. Reported-by: syzbot+b441db1854c360b83221@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=3Db441db1854c360b83221 Fixes: 767e4de3ffce ("gfs2: per-filesystem bufdata cache") Tested-by: syzbot+b441db1854c360b83221@syzkaller.appspotmail.com Signed-off-by: Deepanshu Kartikey --- fs/gfs2/ops_fstype.c | 21 ++++++++++----------- 1 file changed, 10 insertions(+), 11 deletions(-) diff --git a/fs/gfs2/ops_fstype.c b/fs/gfs2/ops_fstype.c index b44adb40635d..7f8e04c11494 100644 --- a/fs/gfs2/ops_fstype.c +++ b/fs/gfs2/ops_fstype.c @@ -1198,17 +1198,9 @@ static int gfs2_fill_super(struct super_block *sb, s= truct fs_context *fc) if (!sdp->sd_delete_wq) goto fail_glock_wq; =20 - char *bufdata_name =3D kasprintf(GFP_KERNEL, "gfs2-bufdata/%s", sdp->sd_f= sname); - sdp->sd_bufdata =3D kmem_cache_create(bufdata_name, - sizeof(struct gfs2_bufdata), - 0, 0, NULL); - kfree(bufdata_name); - if (!sdp->sd_bufdata) - goto fail_delete_wq; - error =3D gfs2_sys_fs_add(sdp); if (error) - goto fail_bufdata; + goto fail_delete_wq; =20 gfs2_create_debugfs_file(sdp); =20 @@ -1255,6 +1247,15 @@ static int gfs2_fill_super(struct super_block *sb, s= truct fs_context *fc) snprintf(sdp->sd_fsname, sizeof(sdp->sd_fsname), "%s.%u", sdp->sd_table_name, sdp->sd_lockstruct.ls_jid); =20 + char *bufdata_name =3D kasprintf(GFP_KERNEL, "gfs2-bufdata/%s", sdp->sd_f= sname); + + sdp->sd_bufdata =3D kmem_cache_create(bufdata_name, + sizeof(struct gfs2_bufdata), + 0, 0, NULL); + kfree(bufdata_name); + if (!sdp->sd_bufdata) + goto fail_sb; + error =3D init_inodes(sdp, DO); if (error) goto fail_sb; @@ -1304,6 +1305,7 @@ static int gfs2_fill_super(struct super_block *sb, st= ruct fs_context *fc) if (sb->s_root) dput(sb->s_root); sb->s_root =3D NULL; + kmem_cache_destroy(sdp->sd_bufdata); fail_locking: init_locking(sdp, &mount_gh, UNDO); fail_lm: @@ -1313,8 +1315,6 @@ static int gfs2_fill_super(struct super_block *sb, st= ruct fs_context *fc) fail_debug: gfs2_delete_debugfs_file(sdp); gfs2_sys_fs_del(sdp); -fail_bufdata: - kmem_cache_destroy(sdp->sd_bufdata); fail_delete_wq: destroy_workqueue(sdp->sd_delete_wq); fail_glock_wq: --=20 2.43.0