From: Jens Axboe axboe@kernel.dk
commit 0b8c0ec7eedcd8f9f1a1f238d87f9b512b09e71a upstream.
syzbot reports:
kasan: CONFIG_KASAN_INLINE enabled kasan: GPF could be caused by NULL-ptr deref or user memory access general protection fault: 0000 [#1] PREEMPT SMP KASAN CPU: 0 PID: 9217 Comm: io_uring-sq Not tainted 5.4.0-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:creds_are_invalid kernel/cred.c:792 [inline] RIP: 0010:__validate_creds include/linux/cred.h:187 [inline] RIP: 0010:override_creds+0x9f/0x170 kernel/cred.c:550 Code: ac 25 00 81 fb 64 65 73 43 0f 85 a3 37 00 00 e8 17 ab 25 00 49 8d 7c 24 10 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <0f> b6 04 02 84 c0 74 08 3c 03 0f 8e 96 00 00 00 41 8b 5c 24 10 bf RSP: 0018:ffff88809c45fda0 EFLAGS: 00010202 RAX: dffffc0000000000 RBX: 0000000043736564 RCX: ffffffff814f3318 RDX: 0000000000000002 RSI: ffffffff814f3329 RDI: 0000000000000010 RBP: ffff88809c45fdb8 R08: ffff8880a3aac240 R09: ffffed1014755849 R10: ffffed1014755848 R11: ffff8880a3aac247 R12: 0000000000000000 R13: ffff888098ab1600 R14: 0000000000000000 R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007ffd51c40664 CR3: 0000000092641000 CR4: 00000000001406f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: io_sq_thread+0x1c7/0xa20 fs/io_uring.c:3274 kthread+0x361/0x430 kernel/kthread.c:255 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352 Modules linked in: ---[ end trace f2e1a4307fbe2245 ]--- RIP: 0010:creds_are_invalid kernel/cred.c:792 [inline] RIP: 0010:__validate_creds include/linux/cred.h:187 [inline] RIP: 0010:override_creds+0x9f/0x170 kernel/cred.c:550 Code: ac 25 00 81 fb 64 65 73 43 0f 85 a3 37 00 00 e8 17 ab 25 00 49 8d 7c 24 10 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <0f> b6 04 02 84 c0 74 08 3c 03 0f 8e 96 00 00 00 41 8b 5c 24 10 bf RSP: 0018:ffff88809c45fda0 EFLAGS: 00010202 RAX: dffffc0000000000 RBX: 0000000043736564 RCX: ffffffff814f3318 RDX: 0000000000000002 RSI: ffffffff814f3329 RDI: 0000000000000010 RBP: ffff88809c45fdb8 R08: ffff8880a3aac240 R09: ffffed1014755849 R10: ffffed1014755848 R11: ffff8880a3aac247 R12: 0000000000000000 R13: ffff888098ab1600 R14: 0000000000000000 R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007ffd51c40664 CR3: 0000000092641000 CR4: 00000000001406f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
which is caused by slab fault injection triggering a failure in prepare_creds(). We don't actually need to create a copy of the creds as we're not modifying it, we just need a reference on the current task creds. This avoids the failure case as well, and propagates the const throughout the stack.
Fixes: 181e448d8709 ("io_uring: async workers should inherit the user creds") Reported-by: syzbot+5320383e16029ba057ff@syzkaller.appspotmail.com Signed-off-by: Jens Axboe axboe@kernel.dk [ only use the io_uring.c portion of the patch - gregkh] Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/io_uring.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -239,7 +239,7 @@ struct io_ring_ctx {
struct user_struct *user;
- struct cred *creds; + const struct cred *creds;
struct completion ctx_done;
@@ -3876,7 +3876,7 @@ static int io_uring_create(unsigned entr ctx->account_mem = account_mem; ctx->user = user;
- ctx->creds = prepare_creds(); + ctx->creds = get_current_cred(); if (!ctx->creds) { ret = -ENOMEM; goto err;