Re: [RFC PATCH 0/2] crypto: caam - fix cts(cbc(aes)) with CAAM driver

["Horia Geantă" <horia.geanta@nxp.com>]

On 6/15/2017 5:57 PM, Horia Geantă wrote:
> On 6/2/2017 3:25 PM, David Gstir wrote:
>> Hi!
>>
>> While testing fscrypt's filename encryption, I noticed that the implementation
>> of cts(cbc(aes)) is broken when the CAAM hardware crypto driver is enabled.
>> Some digging showed that the refactoring of crypto/cts.c in v4.8 
>> (commit 0605c41cc53ca) exposed some problems with CAAM's aes-cbc
>> implementation. This can be tested quite easily by loading the tcrypt
>> module with mode=38. Looks like the cts mode is not used very often
>> and this went unnoticed since 4.8...
>>
>> This patch series is an attempt to fix that and get cts(cbc(aes)) working
>> properly again when the CAAM driver is enabled.
>>
> David, thanks for taking time to fix these.
> 
>> Specifically, the issues are:
[snip]
>> 2) The cts implementation uses aes-cbc twice to perform its job. The second
>>    time, it is called from within the callback of the first call to aes-cbc.
>>    This usage is not properly handled in the CAAM driver which triggers the
>>    BUG below.
>>
> Dan, Radu - have you seen this on i.MX?
> 
>>    My current proposal is to use in_interrupt() to detect such cases and set
>>    the k*alloc flags accordingly. However, since using in_interrupt() is not
>>    really nice, I'm wondering if there is a better way to handle this?
>>
> Nothing else crosses my mind right now, but I'd like to sleep on it.
> 
Herbert,

Commit 0605c41cc53ca ("crypto: cts - Convert to skcipher") appends
CRYPTO_TFM_REQ_MAY_BACKLOG to the original crypto request flags for the
last block - when calling cts_cbc_encrypt().
Is it really needed?

For cts(cbc(aes)) with cbc(aes) offloaded in HW, i.e. running in async
mode, we get the below stack for CAAM driver.
Driver is told that it can sleep (CRYPTO_TFM_REQ_MAY_BACKLOG flag), so
it uses GFP_KERNEL to allocate memory. However, this is incorrect, since
driver runs in atomic context (softirq).

I wouldn't say that:
-David's suggestion - adding in_interrupt()
- or in general: trying to detect in CAAM driver whether we are in
atomic context using anything else than what crypto API provides
(MAY_BACKLOG, MAY_SLEEP flags)

is something we want to do.
IIUC, in general caller (cts / crypto API) is responsible for telling
the callee if it will run in atomic context or not:
https://lwn.net/Articles/274695/

Thanks,
Horia

>> <snip>
>> [  126.252543] BUG: sleeping function called from invalid context at mm/slab.h:432
>> [  126.260099] in_atomic(): 1, irqs_disabled(): 0, pid: 0, name: swapper/0
>> [  126.266837] no locks held by swapper/0/0.
>> [  126.270969] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.12.0-rc3-00052-g0ddec680d395 #287
>> [  126.279226] Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree)
>> [  126.285821] Backtrace:
>> [  126.288406] [<c010c3e4>] (dump_backtrace) from [<c010c690>] (show_stack+0x18/0x1c)
>> [  126.296057]  r7:00000000 r6:60000113 r5:00000000 r4:c102ab48
>> [  126.301798] [<c010c678>] (show_stack) from [<c0427060>] (dump_stack+0xb4/0xe8)
>> [  126.309106] [<c0426fac>] (dump_stack) from [<c014f020>] (___might_sleep+0x17c/0x2a0)
>> [  126.316929]  r9:00000000 r8:c0a016dc r7:c101ee3e r6:000001b0 r5:c0c12fac r4:ffffe000
>> [  126.324751] [<c014eea4>] (___might_sleep) from [<c014f1a8>] (__might_sleep+0x64/0xa4)
>> [  126.332655]  r7:014080c1 r6:00000000 r5:000001b0 r4:c0c12fac
>> [  126.338397] [<c014f144>] (__might_sleep) from [<c0224a20>] (__kmalloc+0x130/0x1b8)
>> [  126.346039]  r6:c071a8ec r5:014080c1 r4:eec01e00
>> [  126.350742] [<c02248f0>] (__kmalloc) from [<c071a8ec>] (ablkcipher_edesc_alloc.constprop.1+0x200/0x900)
>> [  126.360213]  r10:00000000 r9:00000000 r8:c0a016dc r7:c0a016dc r6:ee05ac10 r5:edfdaec0
>> [  126.368109]  r4:00000001 r3:00000020
>> [  126.371765] [<c071a6ec>] (ablkcipher_edesc_alloc.constprop.1) from [<c071b010>] (ablkcipher_encrypt+0x24/0x9c)
>> [  126.381843]  r10:00000000 r9:00000020 r8:00000001 r7:ee05ac10 r6:ed597000 r5:edfdaec0
>> [  126.389738]  r4:ed475d08
>> [  126.392354] [<c071afec>] (ablkcipher_encrypt) from [<c03d6f20>] (skcipher_encrypt_ablkcipher+0x68/0x6c)
>> [  126.401822]  r7:ed475d08 r6:ed597000 r5:00000400 r4:ed475d08
>> [  126.407566] [<c03d6eb8>] (skcipher_encrypt_ablkcipher) from [<c03e8a70>] (cts_cbc_encrypt+0x118/0x124)
>> [  126.416947]  r7:ed475d08 r6:c1001cc0 r5:00000010 r4:edfdae00
>> [  126.422686] [<c03e8958>] (cts_cbc_encrypt) from [<c03e8b88>] (crypto_cts_encrypt_done+0x20/0x54)
>> [  126.431548]  r10:00000000 r9:ee05ac10 r8:00000000 r7:00000010 r6:edc8e6c0 r5:edc8e6d8
>> [  126.439443]  r4:edfdae00
>> [  126.442056] [<c03e8b68>] (crypto_cts_encrypt_done) from [<c07195a0>] (ablkcipher_encrypt_done+0x88/0x9c)
>> [  126.445180] fec 2188000.ethernet eth0: MDIO read timeout
>> [  126.456948]  r5:edc8e6d8 r4:edfdaec0
>> [  126.460604] [<c0719518>] (ablkcipher_encrypt_done) from [<c0715ca0>] (caam_jr_dequeue+0x214/0x2d4)
>> [  126.469639]  r9:00000001 r8:ee088010 r7:000001ff r6:00000001 r5:00000000 r4:edfdaec0
>> [  126.477467] [<c0715a8c>] (caam_jr_dequeue) from [<c012b3f0>] (tasklet_action+0x98/0x154)
>> [  126.485160] fec 2188000.ethernet eth0: MDIO read timeout
>> [  126.490975]  r10:c1080b80 r9:c1008b84 r8:00000000 r7:c1000000 r6:00000000 r5:ee088028
>> [  126.498870]  r4:ee088024
>> [  126.501484] [<c012b358>] (tasklet_action) from [<c012b60c>] (__do_softirq+0xf0/0x2a4)
>> [  126.509390]  r10:40000006 r9:c1002080 r8:00000101 r7:c1002098 r6:c1000000 r5:00000006
>> [  126.517285]  r4:00000000
>> [  126.519896] [<c012b51c>] (__do_softirq) from [<c012bb90>] (irq_exit+0xec/0x168)
>> [  126.525127] fec 2188000.ethernet eth0: MDIO write timeout
>> [  126.532709]  r10:c1008cf0 r9:eec08400 r8:00000001 r7:00000000 r6:c1008b84 r5:00000000
>> [  126.540603]  r4:c0fd940c
>> [  126.543222] [<c012baa4>] (irq_exit) from [<c017ff24>] (__handle_domain_irq+0x74/0xe8)
>> [  126.551135] [<c017feb0>] (__handle_domain_irq) from [<c01015fc>] (gic_handle_irq+0x58/0xbc)
>> [  126.559564]  r9:f4000100 r8:c102af80 r7:c1001ea8 r6:000003ff r5:000003eb r4:f400010c
>> [  126.567384] [<c01015a4>] (gic_handle_irq) from [<c010d2f0>] (__irq_svc+0x70/0x98)
>> [  126.574937] Exception stack(0xc1001ea8 to 0xc1001ef0)
>> [  126.580065] 1ea0:                   00000001 2e39a000 00000000 c100c080 00000000 ef374698
>> [  126.588320] 1ec0: 653b20b1 0000001d 653afed6 0000001d 00000000 c1001f24 c1001ec8 c1001ef8
>> [  126.596568] 1ee0: c016fcf4 c06f1fbc 20000013 ffffffff
>> [  126.601696]  r10:00000000 r9:c1000000 r8:653afed6 r7:c1001edc r6:ffffffff r5:20000013
>> [  126.609591]  r4:c06f1fbc
>> [  126.612210] [<c06f1e34>] (cpuidle_enter_state) from [<c06f2120>] (cpuidle_enter+0x1c/0x20)
>> [  126.620551]  r10:c100f8c0 r9:ef374698 r8:c1008b84 r7:c0fda690 r6:c10089ec r5:c1008a38
>> [  126.628448]  r4:c1000000 r3:ef374698
>> [  126.632114] [<c06f2104>] (cpuidle_enter) from [<c0167330>] (call_cpuidle+0x28/0x44)
>> [  126.639859] [<c0167308>] (call_cpuidle) from [<c0167608>] (do_idle+0x1ac/0x220)
>> [  126.647249] [<c016745c>] (do_idle) from [<c0167a20>] (cpu_startup_entry+0x20/0x24)
>> [  126.654895]  r10:c0e60a50 r9:efffc940 r8:c1080000 r7:c10089c0 r6:c1080000 r5:00000002
>> [  126.662793]  r4:000000bd r3:c0e733c4
>> [  126.666457] [<c0167a00>] (cpu_startup_entry) from [<c09cfbd4>] (rest_init+0x154/0x198)
>> [  126.674463] [<c09cfa80>] (rest_init) from [<c0e00cf0>] (start_kernel+0x344/0x3b8)
>> [  126.682015]  r5:ffffffff r4:c108004c
>> [  126.685668] [<c0e009ac>] (start_kernel) from [<1000807c>] (0x1000807c)
>> </snip>
>>
>>   crypto: caam - properly set IV after {en,de}crypt
>>   crypto: caam - fix k*alloc if called from own cipher callback
>>
>>  drivers/crypto/caam/caamalg.c | 55 +++++++++++++++++++++++++++++++++++--------
>>  1 file changed, 45 insertions(+), 10 deletions(-)
>>