• Jens Axboe's avatar
    io_uring: use current task creds instead of allocating a new one · 0b8c0ec7
    Jens Axboe authored
    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: 181e448d ("io_uring: async workers should inherit the user creds")
    Reported-by: syzbot+5320383e16029ba057ff@syzkaller.appspotmail.com
    Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    0b8c0ec7
io-wq.h 2.98 KB