From: Baokun Li <libaokun1@huawei.com> stable inclusion from stable-v4.19.238 commit c3b07c875fa8f906f932976460fd14798596f101 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/IBP4D9 CVE: CVE-2021-47656 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- commit 4c7c44ee1650677fbe89d86edbad9497b7679b5c upstream. When we mount a jffs2 image, assume that the first few blocks of the image are normal and contain at least one xattr-related inode, but the next block is abnormal. As a result, an error is returned in jffs2_scan_eraseblock(). jffs2_clear_xattr_subsystem() is then called in jffs2_build_filesystem() and then again in jffs2_do_fill_super(). Finally we can observe the following report: ================================================================== BUG: KASAN: use-after-free in jffs2_clear_xattr_subsystem+0x95/0x6ac Read of size 8 at addr ffff8881243384e0 by task mount/719 Call Trace: dump_stack+0x115/0x16b jffs2_clear_xattr_subsystem+0x95/0x6ac jffs2_do_fill_super+0x84f/0xc30 jffs2_fill_super+0x2ea/0x4c0 mtd_get_sb+0x254/0x400 mtd_get_sb_by_nr+0x4f/0xd0 get_tree_mtd+0x498/0x840 jffs2_get_tree+0x25/0x30 vfs_get_tree+0x8d/0x2e0 path_mount+0x50f/0x1e50 do_mount+0x107/0x130 __se_sys_mount+0x1c5/0x2f0 __x64_sys_mount+0xc7/0x160 do_syscall_64+0x45/0x70 entry_SYSCALL_64_after_hwframe+0x44/0xa9 Allocated by task 719: kasan_save_stack+0x23/0x60 __kasan_kmalloc.constprop.0+0x10b/0x120 kasan_slab_alloc+0x12/0x20 kmem_cache_alloc+0x1c0/0x870 jffs2_alloc_xattr_ref+0x2f/0xa0 jffs2_scan_medium.cold+0x3713/0x4794 jffs2_do_mount_fs.cold+0xa7/0x2253 jffs2_do_fill_super+0x383/0xc30 jffs2_fill_super+0x2ea/0x4c0 [...] Freed by task 719: kmem_cache_free+0xcc/0x7b0 jffs2_free_xattr_ref+0x78/0x98 jffs2_clear_xattr_subsystem+0xa1/0x6ac jffs2_do_mount_fs.cold+0x5e6/0x2253 jffs2_do_fill_super+0x383/0xc30 jffs2_fill_super+0x2ea/0x4c0 [...] The buggy address belongs to the object at ffff8881243384b8 which belongs to the cache jffs2_xattr_ref of size 48 The buggy address is located 40 bytes inside of 48-byte region [ffff8881243384b8, ffff8881243384e8) [...] ================================================================== The triggering of the BUG is shown in the following stack: ----------------------------------------------------------- jffs2_fill_super jffs2_do_fill_super jffs2_do_mount_fs jffs2_build_filesystem jffs2_scan_medium jffs2_scan_eraseblock <--- ERROR jffs2_clear_xattr_subsystem <--- free jffs2_clear_xattr_subsystem <--- free again ----------------------------------------------------------- An error is returned in jffs2_do_mount_fs(). If the error is returned by jffs2_sum_init(), the jffs2_clear_xattr_subsystem() does not need to be executed. If the error is returned by jffs2_build_filesystem(), the jffs2_clear_xattr_subsystem() also does not need to be executed again. So move jffs2_clear_xattr_subsystem() from 'out_inohash' to 'out_root' to fix this UAF problem. Fixes: aa98d7cf59b5 ("[JFFS2][XATTR] XATTR support on JFFS2 (version. 5)") Cc: stable@vger.kernel.org Reported-by: Hulk Robot <hulkci@huawei.com> Signed-off-by: Baokun Li <libaokun1@huawei.com> Signed-off-by: Richard Weinberger <richard@nod.at> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Wang Zhaolong <wangzhaolong1@huawei.com> --- fs/jffs2/fs.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/jffs2/fs.c b/fs/jffs2/fs.c index eab04eca95a3..81f7a6efe168 100644 --- a/fs/jffs2/fs.c +++ b/fs/jffs2/fs.c @@ -595,12 +595,12 @@ int jffs2_do_fill_super(struct super_block *sb, void *data, int silent) out_root: jffs2_free_ino_caches(c); jffs2_free_raw_node_refs(c); kvfree(c->blocks); - out_inohash: jffs2_clear_xattr_subsystem(c); + out_inohash: kfree(c->inocache_list); out_wbuf: jffs2_flash_cleanup(c); return ret; -- 2.34.3