[lustre-devel] sec: O_DIRECT for encrypted file crashes Linux client

[NeilBrown]

On Mon, Oct 19 2020, James Simmons wrote:

> I have ported patch https://review.whamcloud.com/38967 which is 
> "lustre: sec: O_DIRECT for encrypted file". The big difference is that for 
> the Linux client we are using the native fscrypto layer. In my testing I'm 
> seeing:
>
> 2020-10-18 15:26:49 [ 4462.081809][T14012] Lustre: DEBUG MARKER: == sanity 
> test 56w: check lfs_migrate -c stripe_count works 
> ========================================== 15:26:49 (1603049209)
> 2020-10-18 15:26:52 [ 4464.514691][T30281] BUG: kernel NULL pointer 
> dereference, address: 0000000000000048
> 2020-10-18 15:26:52 [ 4464.524282][T30281] #PF: supervisor read access in 
> kernel mode
> 2020-10-18 15:26:52 [ 4464.532011][T30281] #PF: error_code(0x0000) - 
> not-present page
> 2020-10-18 15:26:52 [ 4464.539709][T30281] PGD 80000007edcce067 P4D 
> 80000007edcce067 PUD 7f1306067 PMD 0
> 2020-10-18 15:26:52 [ 4464.549144][T30281] Oops: 0000 [#1] PREEMPT SMP PTI
> 2020-10-18 15:26:52 [ 4464.555851][T30281] CPU: 0 PID: 30281 Comm: 
> ptlrpcd_00_04 Tainted: G        W         5.7.0-rc7+ #1
> 2020-10-18 15:26:52 [ 4464.566720][T30281] Hardware name: Supermicro Super 
> Server/To be filled by O.E.M., BIOS 2.0b 08/12/2016
> 2020-10-18 15:26:52 [ 4464.577932][T30281] RIP: 
> 0010:mempool_free+0x12/0x80
> 2020-10-18 15:26:52 [ 4464.584690][T30281] Code: 60 e8 ff cc cc cc cc cc 
> 0f 1f 44 00 00 e9 86 a3 08 00 66 0f 1f 44 00 00 0f 1f 44 00 00 55 48 85 ff 
> 48 89 fd 53 74 1a 48 89 f3 <8b> 46 48 39 46 4c 7c 12 48 8b 73 58 48 8b 43 
> 68 48 89 ef 5b 5d ff
> 2020-10-18 15:26:52 [ 4464.607734][T30281] RSP: 0018:ffffc9002414fcc0 
> EFLAGS: 00010282
> 2020-10-18 15:26:52 [ 4464.615423][T30281] RAX: ffff8887d44fb5e0 RBX: 
> 0000000000000000 RCX: 0000000000000000
> 2020-10-18 15:26:52 [ 4464.625013][T30281] RDX: ffff888845abb780 RSI: 
> 0000000000000000 RDI: ffffea001f553340
> 2020-10-18 15:26:52 [ 4464.634577][T30281] RBP: ffffea001f553340 R08: 
> 0000000000000000 R09: 0000000000000000
> 2020-10-18 15:26:52 [ 4464.644109][T30281] R10: 0000000000000000 R11: 
> 000000000000000f R12: 0000000000000000
> 2020-10-18 15:26:52 [ 4464.653614][T30281] R13: ffff8887d736c9f0 R14: 
> 0000000000000010 R15: ffff888845abb780
> 2020-10-18 15:26:52 [ 4464.663095][T30281] FS:  0000000000000000(0000) 
> GS:ffff88885e600000(0000) knlGS:0000000000000000
> 2020-10-18 15:26:52 [ 4464.673521][T30281] CS:  0010 DS: 0000 ES: 0000 
> CR0: 0000000080050033
> 2020-10-18 15:26:52 [ 4464.681579][T30281] CR2: 0000000000000048 CR3: 
> 00000007cf9fa004 CR4: 00000000001606f0
> 2020-10-18 15:26:52 [ 4464.691015][T30281] Call Trace:
> 2020-10-18 15:26:52 [ 4464.695751][T30281]  brw_interpret+0xac/0xa60 [osc]
> 2020-10-18 15:26:52 [ 4464.702190][T30281]  ? _raw_spin_unlock+0x29/0x50
> 2020-10-18 15:26:52 [ 4464.708490][T30281]  ptlrpc_check_set+0x329/0x1790 
> [ptlrpc]
> 2020-10-18 15:26:52 [ 4464.715599][T30281]  ptlrpcd_check+0x411/0x460 
> [ptlrpc]
> 2020-10-18 15:26:52 [ 4464.722318][T30281]  ptlrpcd+0x278/0x300 [ptlrpc]
> 2020-10-18 15:26:52 [ 4464.728463][T30281]  ? remove_wait_queue+0x60/0x60
> 2020-10-18 15:26:52 [ 4464.734667][T30281]  kthread+0x12a/0x170
> 2020-10-18 15:26:52 [ 4464.739993][T30281]  ? ptlrpcd_check+0x460/0x460 
> [ptlrpc]
> 2020-10-18 15:26:52 [ 4464.746745][T30281]  ? kthread_bind+0x10/0x10
> 2020-10-18 15:26:52 [ 4464.752431][T30281]  ret_from_fork+0x24/0x30
>
> Neil I suspect you might see this as well once this patch is ported to 
> your tree. Any idea why this would break? I haven't dugged down into it 
> yet.

Something has passed a NULL mempool to mempool_free().
Possibly osc_release_bounce_pages -> fscrypt_finalize_bounce_page
   -> fscrypt_free_bounce_page -> mempool_free

The pool is initialized by fscrypt_initialize <-
fscrypt_get_encryption_info.
I don't know why that hasn't been called.

My guess is that this is a rare timing problem and could equally well
happen with the llcrypt code in OpenSFS lustre.
Have you hit this more than once?

NeilBrown
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