On Mon, Dec 30, 2024 at 11:22:28AM -0800, syzbot wrote: > Hello, > > syzbot found the following issue on: > > HEAD commit: a024e377efed net: llc: reset skb->transport_header > git tree: net > console+strace: https://syzkaller.appspot.com/x/log.txt?x=15c7f0b0580000 > kernel config: https://syzkaller.appspot.com/x/.config?x=6a2b862bf4a5409f > dashboard link: https://syzkaller.appspot.com/bug?extid=b3e02953598f447d4d2a > compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14bce818580000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12bce818580000 > > Downloadable assets: > disk image: https://storage.googleapis.com/syzbot-assets/f2ea524d69fe/disk-a024e377.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/b39d227b097d/vmlinux-a024e377.xz > kernel image: https://storage.googleapis.com/syzbot-assets/8ee66636253f/bzImage-a024e377.xz ---8<--- As the null algorithm may be freed in softirq context through af_alg, use spin locks instead of mutexes to protect the default null algorithm. Reported-by: syzbot+b3e02953598f447d4d2a@xxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> diff --git a/crypto/crypto_null.c b/crypto/crypto_null.c index 5b84b0f7cc17..337867028653 100644 --- a/crypto/crypto_null.c +++ b/crypto/crypto_null.c @@ -17,10 +17,10 @@ #include <crypto/internal/skcipher.h> #include <linux/init.h> #include <linux/module.h> -#include <linux/mm.h> +#include <linux/spinlock.h> #include <linux/string.h> -static DEFINE_MUTEX(crypto_default_null_skcipher_lock); +static DEFINE_SPINLOCK(crypto_default_null_skcipher_lock); static struct crypto_sync_skcipher *crypto_default_null_skcipher; static int crypto_default_null_skcipher_refcnt; @@ -152,23 +152,32 @@ MODULE_ALIAS_CRYPTO("cipher_null"); struct crypto_sync_skcipher *crypto_get_default_null_skcipher(void) { + struct crypto_sync_skcipher *ntfm = NULL; struct crypto_sync_skcipher *tfm; - mutex_lock(&crypto_default_null_skcipher_lock); + spin_lock_bh(&crypto_default_null_skcipher_lock); tfm = crypto_default_null_skcipher; if (!tfm) { - tfm = crypto_alloc_sync_skcipher("ecb(cipher_null)", 0, 0); - if (IS_ERR(tfm)) - goto unlock; + spin_unlock_bh(&crypto_default_null_skcipher_lock); - crypto_default_null_skcipher = tfm; + ntfm = crypto_alloc_sync_skcipher("ecb(cipher_null)", 0, 0); + if (IS_ERR(ntfm)) + return ntfm; + + spin_lock_bh(&crypto_default_null_skcipher_lock); + tfm = crypto_default_null_skcipher; + if (!tfm) { + tfm = ntfm; + ntfm = NULL; + crypto_default_null_skcipher = tfm; + } } crypto_default_null_skcipher_refcnt++; + spin_unlock_bh(&crypto_default_null_skcipher_lock); -unlock: - mutex_unlock(&crypto_default_null_skcipher_lock); + crypto_free_sync_skcipher(ntfm); return tfm; } @@ -176,12 +185,16 @@ EXPORT_SYMBOL_GPL(crypto_get_default_null_skcipher); void crypto_put_default_null_skcipher(void) { - mutex_lock(&crypto_default_null_skcipher_lock); + struct crypto_sync_skcipher *tfm = NULL; + + spin_lock_bh(&crypto_default_null_skcipher_lock); if (!--crypto_default_null_skcipher_refcnt) { - crypto_free_sync_skcipher(crypto_default_null_skcipher); + tfm = crypto_default_null_skcipher; crypto_default_null_skcipher = NULL; } - mutex_unlock(&crypto_default_null_skcipher_lock); + spin_unlock_bh(&crypto_default_null_skcipher_lock); + + crypto_free_sync_skcipher(tfm); } EXPORT_SYMBOL_GPL(crypto_put_default_null_skcipher); -- Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
