dm crypt: fix cpu hotplug crash by removing per-cpu structure
The DM crypt target used per-cpu structures to hold pointers to a
ablkcipher_request structure. The code assumed that the work item keeps
executing on a single CPU, so it didn't use synchronization when
accessing this structure.
If a CPU is disabled by writing 0 to /sys/devices/system/cpu/cpu*/online,
the work item could be moved to another CPU. This causes dm-crypt
crashes, like the following, because the code starts using an incorrect
ablkcipher_request:
smpboot: CPU 7 is now offline
BUG: unable to handle kernel NULL pointer dereference at 0000000000000130
IP: [<ffffffffa1862b3d>] crypt_convert+0x12d/0x3c0 [dm_crypt]
...
Call Trace:
[<ffffffffa1864415>] ? kcryptd_crypt+0x305/0x470 [dm_crypt]
[<ffffffff81062060>] ? finish_task_switch+0x40/0xc0
[<ffffffff81052a28>] ? process_one_work+0x168/0x470
[<ffffffff8105366b>] ? worker_thread+0x10b/0x390
[<ffffffff81053560>] ? manage_workers.isra.26+0x290/0x290
[<ffffffff81058d9f>] ? kthread+0xaf/0xc0
[<ffffffff81058cf0>] ? kthread_create_on_node+0x120/0x120
[<ffffffff813464ac>] ? ret_from_fork+0x7c/0xb0
[<ffffffff81058cf0>] ? kthread_create_on_node+0x120/0x120
Fix this bug by removing the per-cpu definition. The structure
ablkcipher_request is accessed via a pointer from convert_context.
Consequently, if the work item is rescheduled to a different CPU, the
thread still uses the same ablkcipher_request.
This change may undermine performance improvements intended by commit
c0297721 ("dm crypt: scale to multiple cpus") on select hardware. In
practice no performance difference was observed on recent hardware. But
regardless, correctness is more important than performance.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org
This commit is contained in:
Mikulas Patocka
Mike Snitzer
Родитель
d6d211db37
Коммит
610f2de355
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@ -19,7 +19,6 @@
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#include <linux/crypto.h>
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#include <linux/workqueue.h>
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#include <linux/backing-dev.h>
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#include <linux/percpu.h>
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#include <linux/atomic.h>
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#include <linux/scatterlist.h>
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#include <asm/page.h>
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@ -43,6 +42,7 @@ struct convert_context {
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struct bvec_iter iter_out;
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sector_t cc_sector;
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atomic_t cc_pending;
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struct ablkcipher_request *req;
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};
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/*
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@ -111,15 +111,7 @@ struct iv_tcw_private {
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enum flags { DM_CRYPT_SUSPENDED, DM_CRYPT_KEY_VALID };
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/*
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* Duplicated per-CPU state for cipher.
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*/
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struct crypt_cpu {
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struct ablkcipher_request *req;
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};
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/*
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* The fields in here must be read only after initialization,
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* changing state should be in crypt_cpu.
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* The fields in here must be read only after initialization.
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*/
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struct crypt_config {
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struct dm_dev *dev;
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@ -150,12 +142,6 @@ struct crypt_config {
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sector_t iv_offset;
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unsigned int iv_size;
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/*
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* Duplicated per cpu state. Access through
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* per_cpu_ptr() only.
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*/
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struct crypt_cpu __percpu *cpu;
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/* ESSIV: struct crypto_cipher *essiv_tfm */
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void *iv_private;
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struct crypto_ablkcipher **tfms;
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@ -192,11 +178,6 @@ static void clone_init(struct dm_crypt_io *, struct bio *);
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static void kcryptd_queue_crypt(struct dm_crypt_io *io);
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static u8 *iv_of_dmreq(struct crypt_config *cc, struct dm_crypt_request *dmreq);
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static struct crypt_cpu *this_crypt_config(struct crypt_config *cc)
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{
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return this_cpu_ptr(cc->cpu);
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}
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/*
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* Use this to access cipher attributes that are the same for each CPU.
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*/
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@ -903,16 +884,15 @@ static void kcryptd_async_done(struct crypto_async_request *async_req,
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static void crypt_alloc_req(struct crypt_config *cc,
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struct convert_context *ctx)
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{
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struct crypt_cpu *this_cc = this_crypt_config(cc);
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unsigned key_index = ctx->cc_sector & (cc->tfms_count - 1);
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if (!this_cc->req)
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this_cc->req = mempool_alloc(cc->req_pool, GFP_NOIO);
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if (!ctx->req)
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ctx->req = mempool_alloc(cc->req_pool, GFP_NOIO);
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ablkcipher_request_set_tfm(this_cc->req, cc->tfms[key_index]);
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ablkcipher_request_set_callback(this_cc->req,
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ablkcipher_request_set_tfm(ctx->req, cc->tfms[key_index]);
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ablkcipher_request_set_callback(ctx->req,
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CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
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kcryptd_async_done, dmreq_of_req(cc, this_cc->req));
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kcryptd_async_done, dmreq_of_req(cc, ctx->req));
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}
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/*
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@ -921,7 +901,6 @@ static void crypt_alloc_req(struct crypt_config *cc,
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static int crypt_convert(struct crypt_config *cc,
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struct convert_context *ctx)
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{
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struct crypt_cpu *this_cc = this_crypt_config(cc);
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int r;
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atomic_set(&ctx->cc_pending, 1);
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@ -932,7 +911,7 @@ static int crypt_convert(struct crypt_config *cc,
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atomic_inc(&ctx->cc_pending);
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r = crypt_convert_block(cc, ctx, this_cc->req);
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r = crypt_convert_block(cc, ctx, ctx->req);
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switch (r) {
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/* async */
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@ -941,7 +920,7 @@ static int crypt_convert(struct crypt_config *cc,
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reinit_completion(&ctx->restart);
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/* fall through*/
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case -EINPROGRESS:
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this_cc->req = NULL;
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ctx->req = NULL;
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ctx->cc_sector++;
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continue;
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@ -1040,6 +1019,7 @@ static struct dm_crypt_io *crypt_io_alloc(struct crypt_config *cc,
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io->sector = sector;
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io->error = 0;
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io->base_io = NULL;
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io->ctx.req = NULL;
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atomic_set(&io->io_pending, 0);
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return io;
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@ -1065,6 +1045,8 @@ static void crypt_dec_pending(struct dm_crypt_io *io)
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if (!atomic_dec_and_test(&io->io_pending))
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return;
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if (io->ctx.req)
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mempool_free(io->ctx.req, cc->req_pool);
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mempool_free(io, cc->io_pool);
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if (likely(!base_io))
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@ -1492,8 +1474,6 @@ static int crypt_wipe_key(struct crypt_config *cc)
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static void crypt_dtr(struct dm_target *ti)
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{
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struct crypt_config *cc = ti->private;
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struct crypt_cpu *cpu_cc;
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int cpu;
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ti->private = NULL;
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@ -1505,13 +1485,6 @@ static void crypt_dtr(struct dm_target *ti)
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if (cc->crypt_queue)
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destroy_workqueue(cc->crypt_queue);
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if (cc->cpu)
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for_each_possible_cpu(cpu) {
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cpu_cc = per_cpu_ptr(cc->cpu, cpu);
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if (cpu_cc->req)
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mempool_free(cpu_cc->req, cc->req_pool);
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}
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crypt_free_tfms(cc);
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if (cc->bs)
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@ -1530,9 +1503,6 @@ static void crypt_dtr(struct dm_target *ti)
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if (cc->dev)
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dm_put_device(ti, cc->dev);
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if (cc->cpu)
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free_percpu(cc->cpu);
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kzfree(cc->cipher);
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kzfree(cc->cipher_string);
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@ -1588,13 +1558,6 @@ static int crypt_ctr_cipher(struct dm_target *ti,
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if (tmp)
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DMWARN("Ignoring unexpected additional cipher options");
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cc->cpu = __alloc_percpu(sizeof(*(cc->cpu)),
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__alignof__(struct crypt_cpu));
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if (!cc->cpu) {
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ti->error = "Cannot allocate per cpu state";
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goto bad_mem;
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}
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/*
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* For compatibility with the original dm-crypt mapping format, if
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* only the cipher name is supplied, use cbc-plain.
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