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Commit 7684bd33 authored by Peng Wang's avatar Peng Wang Committed by Kees Cook
Browse files

pstore: Avoid duplicate call of persistent_ram_zap() 



When initialing a prz, if invalid data is found (no PERSISTENT_RAM_SIG),
the function call path looks like this:

ramoops_init_prz ->
    persistent_ram_new -> persistent_ram_post_init -> persistent_ram_zap
    persistent_ram_zap

As we can see, persistent_ram_zap() is called twice.
We can avoid this by adding an option to persistent_ram_new(), and
only call persistent_ram_zap() when it is needed.

Signed-off-by: default avatarPeng Wang <wangpeng15@xiaomi.com>
[kees: minor tweak to exit path and commit log]
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
parent b77fa617

fs/pstore/ram.c

+1 −3
Original line number Original line Diff line number Diff line
@@ -640,7 +640,7 @@ static int ramoops_init_prz(const char *name, 




	label = kasprintf(GFP_KERNEL, "ramoops:%s", name);

	label = kasprintf(GFP_KERNEL, "ramoops:%s", name);

	*prz = persistent_ram_new(*paddr, sz, sig, &cxt->ecc_info,

	*prz = persistent_ram_new(*paddr, sz, sig, &cxt->ecc_info,

				  cxt->memtype, 0, label);

				  cxt->memtype, PRZ_FLAG_ZAP_OLD, label);

	if (IS_ERR(*prz)) {

	if (IS_ERR(*prz)) {

		int err = PTR_ERR(*prz);

		int err = PTR_ERR(*prz);
@@ -649,8 +649,6 @@ static int ramoops_init_prz(const char *name, 
		return err;

		return err;

	}

	}





	persistent_ram_zap(*prz);



	*paddr += sz;

	*paddr += sz;





	return 0;

	return 0;

fs/pstore/ram_core.c

+9 −6
Original line number Original line Diff line number Diff line
@@ -489,6 +489,7 @@ static int persistent_ram_post_init(struct persistent_ram_zone *prz, u32 sig, 
				    struct persistent_ram_ecc_info *ecc_info)

				    struct persistent_ram_ecc_info *ecc_info)

{

{

	int ret;

	int ret;

	bool zap = !!(prz->flags & PRZ_FLAG_ZAP_OLD);





	ret = persistent_ram_init_ecc(prz, ecc_info);

	ret = persistent_ram_init_ecc(prz, ecc_info);

	if (ret)

	if (ret)
@@ -498,22 +499,24 @@ static int persistent_ram_post_init(struct persistent_ram_zone *prz, u32 sig, 




	if (prz->buffer->sig == sig) {

	if (prz->buffer->sig == sig) {

		if (buffer_size(prz) > prz->buffer_size ||

		if (buffer_size(prz) > prz->buffer_size ||

		    buffer_start(prz) > buffer_size(prz))

		    buffer_start(prz) > buffer_size(prz)) {

			pr_info("found existing invalid buffer, size %zu, start %zu\n",

			pr_info("found existing invalid buffer, size %zu, start %zu\n",

				buffer_size(prz), buffer_start(prz));

				buffer_size(prz), buffer_start(prz));

		else {

			zap = true;

		} else {

			pr_debug("found existing buffer, size %zu, start %zu\n",

			pr_debug("found existing buffer, size %zu, start %zu\n",

				 buffer_size(prz), buffer_start(prz));

				 buffer_size(prz), buffer_start(prz));

			persistent_ram_save_old(prz);

			persistent_ram_save_old(prz);

			return 0;

		}

		}

	} else {

	} else {

		pr_debug("no valid data in buffer (sig = 0x%08x)\n",

		pr_debug("no valid data in buffer (sig = 0x%08x)\n",

			 prz->buffer->sig);

			 prz->buffer->sig);

		prz->buffer->sig = sig;

		zap = true;

	}

	}





	/* Rewind missing or invalid memory area. */

	/* Reset missing, invalid, or single-use memory area. */

	prz->buffer->sig = sig;

	if (zap)

		persistent_ram_zap(prz);

		persistent_ram_zap(prz);





	return 0;

	return 0;

include/linux/pstore_ram.h

+1 −0
Original line number Original line Diff line number Diff line
@@ -30,6 +30,7 @@ 
 * PRZ_FLAG_NO_LOCK is used. For all other cases, locking is required.

 * PRZ_FLAG_NO_LOCK is used. For all other cases, locking is required.

 */

 */

#define PRZ_FLAG_NO_LOCK	BIT(0)

#define PRZ_FLAG_NO_LOCK	BIT(0)

#define PRZ_FLAG_ZAP_OLD	BIT(1)





struct persistent_ram_buffer;

struct persistent_ram_buffer;

struct rs_control;

struct rs_control;