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Message-ID: <CAGXu5jKxFZ17-XuFDxz=qr9o_7KXLg2dh_krN=OQQ+1bFP=qqw@mail.gmail.com> Date: Mon, 19 Jun 2017 12:24:13 -0700 From: Kees Cook <keescook@...omium.org> To: Christoph Hellwig <hch@...radead.org>, David Howells <dhowells@...hat.com> Cc: "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>, Laura Abbott <labbott@...hat.com>, "x86@...nel.org" <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org> Subject: Re: [PATCH v2 07/20] randstruct: Whitelist big_key path struct overloading On Sun, May 28, 2017 at 9:59 AM, Kees Cook <keescook@...omium.org> wrote: > On Sun, May 28, 2017 at 1:12 AM, Christoph Hellwig <hch@...radead.org> wrote: >> What about the untested patch below to just fix the issue? >> >> --- >> From e9eb519c854d2f3d16a4def492577a883246e290 Mon Sep 17 00:00:00 2001 >> From: Christoph Hellwig <hch@....de> >> Date: Sun, 28 May 2017 11:03:34 +0300 >> Subject: security/keys: don't cast union key_payload >> >> Instead store the individual pointers in struct path. >> >> Signed-off-by: Christoph Hellwig <hch@....de> > > Yeah, this is less invasive than what I'd proposed to David to fix it > earlier. David, does this look okay to you? > > Reviewed-by: Kees Cook <keescook@...omium.org> David, if you can Ack this, I'll carry it in my tree. Thanks! -Kees > > -Kees > >> --- >> security/keys/big_key.c | 35 ++++++++++++++++++++--------------- >> 1 file changed, 20 insertions(+), 15 deletions(-) >> >> diff --git a/security/keys/big_key.c b/security/keys/big_key.c >> index 835c1ab30d01..06f2cd07dbd7 100644 >> --- a/security/keys/big_key.c >> +++ b/security/keys/big_key.c >> @@ -26,8 +26,8 @@ >> */ >> enum { >> big_key_data, >> - big_key_path, >> - big_key_path_2nd_part, >> + big_key_path_mnt, >> + big_key_path_dentry, >> big_key_len, >> }; >> >> @@ -118,12 +118,16 @@ static int big_key_crypt(enum big_key_op op, u8 *data, size_t datalen, u8 *key) >> return ret; >> } >> >> +#define PATH_FROM_PAYLOAD(p) { \ >> + .mnt = (p)->data[big_key_path_mnt], \ >> + .dentry = (p)->data[big_key_path_dentry], \ >> +} >> + >> /* >> * Preparse a big key >> */ >> int big_key_preparse(struct key_preparsed_payload *prep) >> { >> - struct path *path = (struct path *)&prep->payload.data[big_key_path]; >> struct file *file; >> u8 *enckey; >> u8 *data = NULL; >> @@ -190,9 +194,10 @@ int big_key_preparse(struct key_preparsed_payload *prep) >> /* Pin the mount and dentry to the key so that we can open it again >> * later >> */ >> + path_get(&file->f_path); >> prep->payload.data[big_key_data] = enckey; >> - *path = file->f_path; >> - path_get(path); >> + prep->payload.data[big_key_path_mnt] = file->f_path.mnt; >> + prep->payload.data[big_key_path_dentry] = file->f_path.dentry; >> fput(file); >> kfree(data); >> } else { >> @@ -222,9 +227,9 @@ int big_key_preparse(struct key_preparsed_payload *prep) >> void big_key_free_preparse(struct key_preparsed_payload *prep) >> { >> if (prep->datalen > BIG_KEY_FILE_THRESHOLD) { >> - struct path *path = (struct path *)&prep->payload.data[big_key_path]; >> + struct path path = PATH_FROM_PAYLOAD(&prep->payload); >> >> - path_put(path); >> + path_put(&path); >> } >> kfree(prep->payload.data[big_key_data]); >> } >> @@ -235,13 +240,13 @@ void big_key_free_preparse(struct key_preparsed_payload *prep) >> */ >> void big_key_revoke(struct key *key) >> { >> - struct path *path = (struct path *)&key->payload.data[big_key_path]; >> + struct path path = PATH_FROM_PAYLOAD(&key->payload); >> >> /* clear the quota */ >> key_payload_reserve(key, 0); >> if (key_is_instantiated(key) && >> (size_t)key->payload.data[big_key_len] > BIG_KEY_FILE_THRESHOLD) >> - vfs_truncate(path, 0); >> + vfs_truncate(&path, 0); >> } >> >> /* >> @@ -252,11 +257,11 @@ void big_key_destroy(struct key *key) >> size_t datalen = (size_t)key->payload.data[big_key_len]; >> >> if (datalen > BIG_KEY_FILE_THRESHOLD) { >> - struct path *path = (struct path *)&key->payload.data[big_key_path]; >> + struct path path = PATH_FROM_PAYLOAD(&key->payload); >> >> - path_put(path); >> - path->mnt = NULL; >> - path->dentry = NULL; >> + path_put(&path); >> + key->payload.data[big_key_path_mnt] = NULL; >> + key->payload.data[big_key_path_dentry] = NULL; >> } >> kfree(key->payload.data[big_key_data]); >> key->payload.data[big_key_data] = NULL; >> @@ -290,7 +295,7 @@ long big_key_read(const struct key *key, char __user *buffer, size_t buflen) >> return datalen; >> >> if (datalen > BIG_KEY_FILE_THRESHOLD) { >> - struct path *path = (struct path *)&key->payload.data[big_key_path]; >> + struct path path = PATH_FROM_PAYLOAD(&key->payload); >> struct file *file; >> u8 *data; >> u8 *enckey = (u8 *)key->payload.data[big_key_data]; >> @@ -300,7 +305,7 @@ long big_key_read(const struct key *key, char __user *buffer, size_t buflen) >> if (!data) >> return -ENOMEM; >> >> - file = dentry_open(path, O_RDONLY, current_cred()); >> + file = dentry_open(&path, O_RDONLY, current_cred()); >> if (IS_ERR(file)) { >> ret = PTR_ERR(file); >> goto error; >> -- >> 2.11.0 >> > > > > -- > Kees Cook > Pixel Security -- Kees Cook Pixel Security
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