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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: Peng Wang <wangpeng15@xiaomi.com>
[kees: minor tweak to exit path and commit log]
Signed-off-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Peng Wang 2018-10-30 15:52:34 +08:00 committed by Kees Cook
parent b77fa617a2
commit 7684bd334d
3 changed files with 11 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
fs/pstore/ram.c
View File

@ -640,7 +640,7 @@ static int ramoops_init_prz(const char *name,
label = kasprintf(GFP_KERNEL, "ramoops:%s", name);
*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)) {
int err = PTR_ERR(*prz);
@ -649,8 +649,6 @@ static int ramoops_init_prz(const char *name,
return err;
}
persistent_ram_zap(*prz);
*paddr += sz;
return 0;

15
fs/pstore/ram_core.c
View File

@ -489,6 +489,7 @@ static int persistent_ram_post_init(struct persistent_ram_zone *prz, u32 sig,
struct persistent_ram_ecc_info *ecc_info)
{
int ret;
bool zap = !!(prz->flags & PRZ_FLAG_ZAP_OLD);
ret = persistent_ram_init_ecc(prz, ecc_info);
if (ret)
@ -498,23 +499,25 @@ static int persistent_ram_post_init(struct persistent_ram_zone *prz, u32 sig,
if (prz->buffer->sig == sig) {
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",
buffer_size(prz), buffer_start(prz));
else {
zap = true;
} else {
pr_debug("found existing buffer, size %zu, start %zu\n",
buffer_size(prz), buffer_start(prz));
persistent_ram_save_old(prz);
return 0;
}
} else {
pr_debug("no valid data in buffer (sig = 0x%08x)\n",
prz->buffer->sig);
prz->buffer->sig = sig;
zap = true;
}
/* Rewind missing or invalid memory area. */
prz->buffer->sig = sig;
persistent_ram_zap(prz);
/* Reset missing, invalid, or single-use memory area. */
if (zap)
persistent_ram_zap(prz);
return 0;
}

1
include/linux/pstore_ram.h
View File

@ -30,6 +30,7 @@
* PRZ_FLAG_NO_LOCK is used. For all other cases, locking is required.
*/
#define PRZ_FLAG_NO_LOCK BIT(0)
#define PRZ_FLAG_ZAP_OLD BIT(1)
struct persistent_ram_buffer;
struct rs_control;