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Date: Wed, 17 Oct 2018 21:44:01 -0700
From: Kees Cook <keescook@...omium.org>
To: Joel Fernandes <joel@...lfernandes.org>
Cc: Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] pstore: Refactor compression initialization
On Wed, Oct 17, 2018 at 6:30 PM, Joel Fernandes <joel@...lfernandes.org> wrote:
> On Wed, Oct 17, 2018 at 02:41:24PM -0700, Kees Cook wrote:
>> With compression initialization now separated from pstore_register(),
>> there is no longer a good reason to do compression method selection
>> during fs init. Instead, merge everything together into the late init.
>> Additionally cleans up the reporting to be more clear.
>>
>> Signed-off-by: Kees Cook <keescook@...omium.org>
>> ---
>> This patch goes on top of Joel's. I'll have both in linux-next shortly...
>> ---
>> fs/pstore/inode.c | 2 --
>> fs/pstore/internal.h | 3 --
>> fs/pstore/platform.c | 65 ++++++++++++++++++++++++++++----------------
>> 3 files changed, 41 insertions(+), 29 deletions(-)
>>
>> diff --git a/fs/pstore/inode.c b/fs/pstore/inode.c
>> index 5fcb845b9fec..d814723fb27d 100644
>> --- a/fs/pstore/inode.c
>> +++ b/fs/pstore/inode.c
>> @@ -486,8 +486,6 @@ static int __init init_pstore_fs(void)
>> {
>> int err;
>>
>> - pstore_choose_compression();
>> -
>> /* Create a convenient mount point for people to access pstore */
>> err = sysfs_create_mount_point(fs_kobj, "pstore");
>> if (err)
>> diff --git a/fs/pstore/internal.h b/fs/pstore/internal.h
>> index fb767e28aeb2..c029314478fa 100644
>> --- a/fs/pstore/internal.h
>> +++ b/fs/pstore/internal.h
>> @@ -37,7 +37,4 @@ extern bool pstore_is_mounted(void);
>> extern void pstore_record_init(struct pstore_record *record,
>> struct pstore_info *psi);
>>
>> -/* Called during module_init() */
>> -extern void __init pstore_choose_compression(void);
>> -
>> #endif
>> diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
>> index f09066db2d4d..e4737a5fa68c 100644
>> --- a/fs/pstore/platform.c
>> +++ b/fs/pstore/platform.c
>> @@ -274,36 +274,56 @@ static int pstore_decompress(void *in, void *out,
>>
>> static void allocate_buf_for_compression(void)
>> {
>> + struct crypto_comp *ctx;
>> + int size;
>> + char *buf;
>> +
>> + /* Skip if not built-in or compression backend not selected yet. */
>> if (!IS_ENABLED(CONFIG_PSTORE_COMPRESS) || !zbackend)
>> return;
>>
>> + /* Skip if no pstore backend yet or compression init already done. */
>> + if (!psinfo || tfm)
>> + return;
>> +
>> if (!crypto_has_comp(zbackend->name, 0, 0)) {
>> - pr_err("No %s compression\n", zbackend->name);
>> + pr_err("Unknown compression: %s\n", zbackend->name);
>> return;
>> }
>>
>> - big_oops_buf_sz = zbackend->zbufsize(psinfo->bufsize);
>> - if (big_oops_buf_sz <= 0)
>> + size = zbackend->zbufsize(psinfo->bufsize);
>> + if (size <= 0) {
>> + pr_err("Invalid compression size for %s: %d\n",
>> + zbackend->name, size);
>> return;
>> + }
>>
>> - big_oops_buf = kmalloc(big_oops_buf_sz, GFP_KERNEL);
>> - if (!big_oops_buf) {
>> - pr_err("allocate compression buffer error!\n");
>> + buf = kmalloc(size, GFP_KERNEL);
>> + if (!buf) {
>> + pr_err("Failed %d byte compression buffer allocation for: %s\n",
>> + size, zbackend->name);
>> return;
>> }
>>
>> - tfm = crypto_alloc_comp(zbackend->name, 0, 0);
>> - if (IS_ERR_OR_NULL(tfm)) {
>> - kfree(big_oops_buf);
>> - big_oops_buf = NULL;
>> - pr_err("crypto_alloc_comp() failed!\n");
>> + ctx = crypto_alloc_comp(zbackend->name, 0, 0);
>> + if (IS_ERR_OR_NULL(ctx)) {
>> + kfree(buf);
>> + pr_err("crypto_alloc_comp('%s') failed: %ld\n", zbackend->name,
>> + PTR_ERR(ctx));
>> return;
>> }
>> +
>> + /* A non-NULL big_oops_buf indicates compression is available. */
>> + tfm = ctx;
>> + big_oops_buf_sz = size;
>> + big_oops_buf = buf;
>> +
>> + pr_info("Using compression: %s\n", zbackend->name);
>> }
>>
>> static void free_buf_for_compression(void)
>> {
>> - if (IS_ENABLED(CONFIG_PSTORE_COMPRESS) && !IS_ERR_OR_NULL(tfm))
>> + if (IS_ENABLED(CONFIG_PSTORE_COMPRESS) && tfm)
>> crypto_free_comp(tfm);
>> kfree(big_oops_buf);
>> big_oops_buf = NULL;
>> @@ -764,31 +784,28 @@ static void pstore_timefunc(struct timer_list *unused)
>> jiffies + msecs_to_jiffies(pstore_update_ms));
>> }
>>
>> -void __init pstore_choose_compression(void)
>> +static int __init pstore_compression_late_init(void)
>> {
>> const struct pstore_zbackend *step;
>>
>> if (!compress)
>> - return;
>> + return 0;
>>
>> + /* Locate desired compression method. */
>> for (step = zbackends; step->name; step++) {
>> if (!strcmp(compress, step->name)) {
>> zbackend = step;
>> - pr_info("using %s compression\n", zbackend->name);
>> - return;
>> + break;
>> }
>> }
>> -}
>>
>> -static int __init pstore_compression_late_init(void)
>> -{
>> /*
>> - * Check if any pstore backends registered earlier but did not allocate
>> - * for compression because crypto was not ready, if so then initialize
>> - * compression.
>> + * Check if any pstore backends registered earlier but did not
>> + * initialize compression because crypto was not ready. If so,
>> + * then initialize compression now.
>> */
>> - if (psinfo && !tfm)
>> - allocate_buf_for_compression();
>> + allocate_buf_for_compression();
>
> We can also get rid of the 'zbackend' global variable since choosing the
> compression backend and allocating the buffers are done at the same time?
That's my intention once I push the zbufsize functions up into the
crypto subsystem (there's a separate series for this that I need to
refresh).
> Otherwise looks good to me,
>
> Reviewed-by: Joel Fernandes (Google) <joel@...lfernandes.org>
Thanks!
-Kees
--
Kees Cook
Pixel Security
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