The patch below does not apply to the 5.10-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From a61df3c413e49b0042f9caf774c58512d1cc71b7 Mon Sep 17 00:00:00 2001

From: Jamie Iles jamie@nuviainc.com Date: Mon, 12 Oct 2020 14:12:04 +0100 Subject: [PATCH] jffs2: Fix NULL pointer dereference in rp_size fs option parsing

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

diff --git a/fs/jffs2/super.c b/fs/jffs2/super.c index c523adaca79f..81ca58c10b72 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);