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Revert "evm: Fix memleak in init_desc"

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commit 51dd64bb99e4478fc5280171acd8e1b529eadaf7 upstream.

This reverts commit ccf11dbaa07b328fa469415c362d33459c140a37.

Commit ccf11dbaa07b ("evm: Fix memleak in init_desc") said there is
memleak in init_desc. That may be incorrect, as we can see, tmp_tfm is
saved in one of the two global variables hmac_tfm or evm_tfm[hash_algo],
then if init_desc is called next time, there is no need to alloc tfm
again, so in the error path of kmalloc desc or crypto_shash_init(desc),
It is not a problem without freeing tmp_tfm.

And also that commit did not reset the global variable to NULL after
freeing tmp_tfm and this makes *tfm a dangling pointer which may cause a
UAF issue.

Reported-by: Guozihua (Scott) <guozihua@huawei.com>
Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Xiu Jianfeng 2022-05-27 19:17:26 +08:00 committed by Greg Kroah-Hartman
parent d85d19f3b6
commit 31e99fa969
1 changed files with 2 additions and 5 deletions
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7
security/integrity/evm/evm_crypto.c
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@ -75,7 +75,7 @@ static struct shash_desc *init_desc(char type, uint8_t hash_algo)
{ {
long rc; long rc;
const char *algo; const char *algo;
struct crypto_shash **tfm, *tmp_tfm = NULL; struct crypto_shash **tfm, *tmp_tfm;
struct shash_desc *desc; struct shash_desc *desc;
if (type == EVM_XATTR_HMAC) { if (type == EVM_XATTR_HMAC) {
@ -120,16 +120,13 @@ unlock:
alloc: alloc:
desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(*tfm), desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(*tfm),
GFP_KERNEL); GFP_KERNEL);
if (!desc) { if (!desc)
crypto_free_shash(tmp_tfm);
return ERR_PTR(-ENOMEM); return ERR_PTR(-ENOMEM);
}
desc->tfm = *tfm; desc->tfm = *tfm;
rc = crypto_shash_init(desc); rc = crypto_shash_init(desc);
if (rc) { if (rc) {
crypto_free_shash(tmp_tfm);
kfree(desc); kfree(desc);
return ERR_PTR(rc); return ERR_PTR(rc);
} }