pstore/ram: Regularize prz label allocation lifetime (e163fdb3) · Commits · 戴 / test

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: ("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>

fs/pstore/ram.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -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;
		}

fs/pstore/ram_core.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -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)

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