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pstore/ram: Regularize prz label allocation lifetime 

In my attempt to fix a memory leak, I introduced a double-free in the
pstore error path. Instead of trying to manage the allocation lifetime
between persistent_ram_new() and its callers, adjust the logic so
persistent_ram_new() always takes a kstrdup() copy, and leaves the
caller's allocation lifetime up to the caller. Therefore callers are
_always_ responsible for freeing their label. Before, it only needed
freeing when the prz itself failed to allocate, and not in any of the
other prz failure cases, which callers would have no visibility into,
which is the root design problem that lead to both the leak and now
double-free bugs.

Reported-by: Cengiz Can <cengiz@kernel.wtf>
Link: https://lore.kernel.org/lkml/d4ec59002ede4aaf9928c7f7526da87c@kernel.wtf
Fixes: 8df955a32a ("pstore/ram: Fix error-path memory leak in persistent_ram_new() callers")
Cc: stable@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Kees Cook 2020-01-08 10:06:54 -08:00
parent 9e5f1c1980
commit e163fdb3f7
2 changed files with 3 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
fs/pstore/ram.c
View File

@ -583,12 +583,12 @@ static int ramoops_init_przs(const char *name,
prz_ar[i] = persistent_ram_new(*paddr, zone_sz, sig,
&cxt->ecc_info,
cxt->memtype, flags, label);
kfree(label);
if (IS_ERR(prz_ar[i])) {
err = PTR_ERR(prz_ar[i]);
dev_err(dev, "failed to request %s mem region (0x%zx@0x%llx): %d\n",
name, record_size,
(unsigned long long)*paddr, err);
kfree(label);
while (i > 0) {
i--;
@ -629,12 +629,12 @@ 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, PRZ_FLAG_ZAP_OLD, label);
kfree(label);
if (IS_ERR(*prz)) {
int err = PTR_ERR(*prz);
dev_err(dev, "failed to request %s mem region (0x%zx@0x%llx): %d\n",
name, sz, (unsigned long long)*paddr, err);
kfree(label);
return err;
}

2
fs/pstore/ram_core.c
View File

@ -574,7 +574,7 @@ struct persistent_ram_zone *persistent_ram_new(phys_addr_t start, size_t size,
/* Initialize general buffer state. */
raw_spin_lock_init(&prz->buffer_lock);
prz->flags = flags;
prz->label = label;
prz->label = kstrdup(label, GFP_KERNEL);
ret = persistent_ram_buffer_map(start, size, prz, memtype);
if (ret)