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pstore/ram: Regularize prz label allocation lifetime

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commit e163fdb3f7f8c62dccf194f3f37a7bcb3c333aa8 upstream.

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: 8df955a32a73 ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Kees Cook 2020-01-08 10:06:54 -08:00 committed by Greg Kroah-Hartman
parent 85b60d3221
commit c617a3b777
2 changed files with 3 additions and 3 deletions
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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)