From 55cbc2564ab2fd555ec0fc39311a9cfb811d7da5 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Wed, 14 Oct 2020 07:35:57 -0600 Subject: [PATCH] io_uring: fix error path cleanup in io_sqe_files_register() syzbot reports the following crash: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] CPU: 1 PID: 8927 Comm: syz-executor.3 Not tainted 5.9.0-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:io_file_from_index fs/io_uring.c:5963 [inline] RIP: 0010:io_sqe_files_register fs/io_uring.c:7369 [inline] RIP: 0010:__io_uring_register fs/io_uring.c:9463 [inline] RIP: 0010:__do_sys_io_uring_register+0x2fd2/0x3ee0 fs/io_uring.c:9553 Code: ec 03 49 c1 ee 03 49 01 ec 49 01 ee e8 57 61 9c ff 41 80 3c 24 00 0f 85 9b 09 00 00 4d 8b af b8 01 00 00 4c 89 e8 48 c1 e8 03 <80> 3c 28 00 0f 85 76 09 00 00 49 8b 55 00 89 d8 c1 f8 09 48 98 4c RSP: 0018:ffffc90009137d68 EFLAGS: 00010246 RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffc9000ef2a000 RDX: 0000000000040000 RSI: ffffffff81d81dd9 RDI: 0000000000000005 RBP: dffffc0000000000 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffffed1012882a37 R13: 0000000000000000 R14: ffffed1012882a38 R15: ffff888094415000 FS: 00007f4266f3c700(0000) GS:ffff8880ae500000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000000000118c000 CR3: 000000008e57d000 CR4: 00000000001506e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x45de59 Code: 0d b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 db b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007f4266f3bc78 EFLAGS: 00000246 ORIG_RAX: 00000000000001ab RAX: ffffffffffffffda RBX: 00000000000083c0 RCX: 000000000045de59 RDX: 0000000020000280 RSI: 0000000000000002 RDI: 0000000000000005 RBP: 000000000118bf68 R08: 0000000000000000 R09: 0000000000000000 R10: 40000000000000a1 R11: 0000000000000246 R12: 000000000118bf2c R13: 00007fff2fa4f12f R14: 00007f4266f3c9c0 R15: 000000000118bf2c Modules linked in: ---[ end trace 2a40a195e2d5e6e6 ]--- RIP: 0010:io_file_from_index fs/io_uring.c:5963 [inline] RIP: 0010:io_sqe_files_register fs/io_uring.c:7369 [inline] RIP: 0010:__io_uring_register fs/io_uring.c:9463 [inline] RIP: 0010:__do_sys_io_uring_register+0x2fd2/0x3ee0 fs/io_uring.c:9553 Code: ec 03 49 c1 ee 03 49 01 ec 49 01 ee e8 57 61 9c ff 41 80 3c 24 00 0f 85 9b 09 00 00 4d 8b af b8 01 00 00 4c 89 e8 48 c1 e8 03 <80> 3c 28 00 0f 85 76 09 00 00 49 8b 55 00 89 d8 c1 f8 09 48 98 4c RSP: 0018:ffffc90009137d68 EFLAGS: 00010246 RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffc9000ef2a000 RDX: 0000000000040000 RSI: ffffffff81d81dd9 RDI: 0000000000000005 RBP: dffffc0000000000 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffffed1012882a37 R13: 0000000000000000 R14: ffffed1012882a38 R15: ffff888094415000 FS: 00007f4266f3c700(0000) GS:ffff8880ae400000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000000000074a918 CR3: 000000008e57d000 CR4: 00000000001506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 which is a copy of fget failure condition jumping to cleanup, but the cleanup requires ctx->file_data to be assigned. Assign it when setup, and ensure that we clear it again for the error path exit. Fixes: 5398ae698525 ("io_uring: clean file_data access in files_register") Reported-by: syzbot+f4ebcc98223dafd8991e@syzkaller.appspotmail.com Signed-off-by: Jens Axboe --- fs/io_uring.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/fs/io_uring.c b/fs/io_uring.c index 94a66a6d1cba..21c6ce15b751 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -7289,6 +7289,7 @@ static int io_sqe_files_register(struct io_ring_ctx *ctx, void __user *arg, if (io_sqe_alloc_file_tables(file_data, nr_tables, nr_args)) goto out_ref; + ctx->file_data = file_data; for (i = 0; i < nr_args; i++, ctx->nr_user_files++) { struct fixed_file_table *table; @@ -7323,7 +7324,6 @@ static int io_sqe_files_register(struct io_ring_ctx *ctx, void __user *arg, table->files[index] = file; } - ctx->file_data = file_data; ret = io_sqe_files_scm(ctx); if (ret) { io_sqe_files_unregister(ctx); @@ -7356,6 +7356,7 @@ out_ref: out_free: kfree(file_data->table); kfree(file_data); + ctx->file_data = NULL; return ret; }