[PATCH 5.10 09/63] jffs2: Fix NULL pointer dereference in rp_size fs option parsing

Greg Kroah-Hartman
2021-01-04T16:06:21Z

From: Jamie Iles <jamie@nuviainc.com>

[ Upstream commit a61df3c413e49b0042f9caf774c58512d1cc71b7 ]

syzkaller found the following JFFS2 splat:

Unable to handle kernel paging request at virtual address dfffa00000000001
Mem abort info:
ESR = 0x96000004
EC = 0x25: DABT (current EL), IL = 32 bits
SET = 0, FnV = 0
EA = 0, S1PTW = 0
Data abort info:
ISV = 0, ISS = 0x00000004
CM = 0, WnR = 0
[dfffa00000000001] address between user and kernel address ranges
Internal error: Oops: 96000004 [#1] SMP
Dumping ftrace buffer:
(ftrace buffer empty)
Modules linked in:
CPU: 0 PID: 12745 Comm: syz-executor.5 Tainted: G S 5.9.0-rc8+ #98
Hardware name: linux,dummy-virt (DT)
pstate: 20400005 (nzCv daif +PAN -UAO BTYPE=--)
pc : jffs2_parse_param+0x138/0x308 fs/jffs2/super.c:206
lr : jffs2_parse_param+0x108/0x308 fs/jffs2/super.c:205
sp : ffff000022a57910
x29: ffff000022a57910 x28: 0000000000000000
x27: ffff000057634008 x26: 000000000000d800
x25: 000000000000d800 x24: ffff0000271a9000
x23: ffffa0001adb5dc0 x22: ffff000023fdcf00
x21: 1fffe0000454af2c x20: ffff000024cc9400
x19: 0000000000000000 x18: 0000000000000000
x17: 0000000000000000 x16: ffffa000102dbdd0
x15: 0000000000000000 x14: ffffa000109e44bc
x13: ffffa00010a3a26c x12: ffff80000476e0b3
x11: 1fffe0000476e0b2 x10: ffff80000476e0b2
x9 : ffffa00010a3ad60 x8 : ffff000023b70593
x7 : 0000000000000003 x6 : 00000000f1f1f1f1
x5 : ffff000023fdcf00 x4 : 0000000000000002
x3 : ffffa00010000000 x2 : 0000000000000001
x1 : dfffa00000000000 x0 : 0000000000000008
Call trace:
jffs2_parse_param+0x138/0x308 fs/jffs2/super.c:206
vfs_parse_fs_param+0x234/0x4e8 fs/fs_context.c:117
vfs_parse_fs_string+0xe8/0x148 fs/fs_context.c:161
generic_parse_monolithic+0x17c/0x208 fs/fs_context.c:201
parse_monolithic_mount_data+0x7c/0xa8 fs/fs_context.c:649
do_new_mount fs/namespace.c:2871 [inline]
path_mount+0x548/0x1da8 fs/namespace.c:3192
do_mount+0x124/0x138 fs/namespace.c:3205
__do_sys_mount fs/namespace.c:3413 [inline]
__se_sys_mount fs/namespace.c:3390 [inline]
__arm64_sys_mount+0x164/0x238 fs/namespace.c:3390
__invoke_syscall arch/arm64/kernel/syscall.c:36 [inline]
invoke_syscall arch/arm64/kernel/syscall.c:48 [inline]
el0_svc_common.constprop.0+0x15c/0x598 arch/arm64/kernel/syscall.c:149
do_el0_svc+0x60/0x150 arch/arm64/kernel/syscall.c:195
el0_svc+0x34/0xb0 arch/arm64/kernel/entry-common.c:226
el0_sync_handler+0xc8/0x5b4 arch/arm64/kernel/entry-common.c:236
el0_sync+0x15c/0x180 arch/arm64/kernel/entry.S:663
Code: d2d40001 f2fbffe1 91002260 d343fc02 (38e16841)
---[ end trace 4edf690313deda44 ]---

This is because since ec10a24f10c8, the option parsing happens before
fill_super and so the MTD device isn't associated with the filesystem.
Defer the size check until there is a valid association.

Fixes: ec10a24f10c8 ("vfs: Convert jffs2 to use the new mount API")
Cc: <stable@vger.kernel.org>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Jamie Iles <jamie@nuviainc.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/jffs2/super.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/fs/jffs2/super.c b/fs/jffs2/super.c
index c523adaca79f3..81ca58c10b728 100644
--- a/fs/jffs2/super.c
+++ b/fs/jffs2/super.c
@@ -202,12 +202,8 @@ static int jffs2_parse_param(struct fs_context *fc, struct fs_parameter *param)
case Opt_rp_size:
if (result.uint_32 > UINT_MAX / 1024)
return invalf(fc, "jffs2: rp_size unrepresentable");
- opt = result.uint_32 * 1024;
- if (opt > c->mtd->size)
- return invalf(fc, "jffs2: Too large reserve pool specified, max is %llu KB",
- c->mtd->size / 1024);
+ c->mount_opts.rp_size = result.uint_32 * 1024;
c->mount_opts.set_rp_size = true;
- c->mount_opts.rp_size = opt;
break;
default:
return -EINVAL;
@@ -269,6 +265,10 @@ static int jffs2_fill_super(struct super_block *sb, struct fs_context *fc)
c->mtd = sb->s_mtd;
c->os_priv = sb;

+ if (c->mount_opts.rp_size > c->mtd->size)
+ return invalf(fc, "jffs2: Too large reserve pool specified, max is %llu KB",
+ c->mtd->size / 1024);
+
/* Initialize JFFS2 superblock locks, the further initialization will
* be done later */
mutex_init(&c->alloc_sem);
--
2.27.0