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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id s30-20020a63925e000000b00477def759cbsm5933519pgn.58.2022.12.07.16.02.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 07 Dec 2022 16:02:15 -0800 (PST) From: Kees Cook To: Jakub Kicinski Cc: Kees Cook , syzbot+fda18eaa8c12534ccb3b@syzkaller.appspotmail.com, Eric Dumazet , "David S. Miller" , Paolo Abeni , Pavel Begunkov , pepsipu , Vlastimil Babka , kasan-dev , Andrii Nakryiko , ast@kernel.org, bpf , Daniel Borkmann , Hao Luo , Jesper Dangaard Brouer , John Fastabend , jolsa@kernel.org, KP Singh , martin.lau@linux.dev, Stanislav Fomichev , song@kernel.org, Yonghong Song , netdev@vger.kernel.org, LKML , Rasesh Mody , Ariel Elior , Manish Chopra , Menglong Dong , David Ahern , Richard Gobert , David Rientjes , Andrey Konovalov , GR-Linux-NIC-Dev@marvell.com, linux-hardening@vger.kernel.org Subject: [PATCH net-next v2] skbuff: Introduce slab_build_skb() Date: Wed, 7 Dec 2022 16:02:13 -0800 Message-Id: <20221208000209.gonna.368-kees@kernel.org> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=6532; h=from:subject:message-id; bh=I5zpjdf6giyPTGWK3waT0b1aZ9hEwojgcygujraz8dc=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBjkSmEkOgkOZcWwciYH5GLWV3obftsCrvUcG4e847b Bi5nkbGJAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCY5EphAAKCRCJcvTf3G3AJrfZD/ 9J2X/Gw9ncWI4dk8wA/WdzHwO05CFaHzRpUpXr+GMG8xWhch5i+SxqJDXVTzXb0YA7TXlpkO9D+otk 5R29AmizYM7EXsl1yZeyMbGQ5hpAufcuX82qAOIodz/lW3bzrzs21vRcUZLrwoV/Fyw0pxzHY5Pf5h ph+jxiId3DghZjSkowXYtsPGXEcnWxRVtUdTcXIwi4Ry8XvyJpqk0jOBV7ZnM8kEJVJ6pUgNjdt61c Gdhjag0bgthVFgM2mpz/QmavD+S+3QlwLB9a3DoVWUJOKJTSQrHNNzbygYMoN5RqmnPz+OcqVneI4E +XcJ6Dh3/v1qbD+rVNET9u/b3bPLy/x06rWB8dgrKn0P/mb601uzlKCKhmm1TG24z1Z9h8w366AVA7 9dU9EwQINOJTDi6NUYcnGa3GApoKuVGCZ03C9xewFJ6BfCrj5qjwQT7CGTH5Vug9puDgl7rBqlIskS WiKGOdtd2hO+BdD3ggipo0i6+bmO07sYVTvcUDv/6GsZZyUy8jET1YpxQS6KU6pKyabXunytY0XNDN o2/3jZeX+Q1xeLy+ge8aeZvS6ypBvKHk51BiHlDd+HM/Ea0wvyjuZr6d5xnNwg9UqO3Po4lIYkKctJ kXJR6WE6EASTgDFD1Xdp19J2MB65NyB2AMFRRTo2I8Nk6cmA+N6Z+5R+M5Sg== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" syzkaller reported: BUG: KASAN: slab-out-of-bounds in __build_skb_around+0x235/0x340 net/core= /skbuff.c:294 Write of size 32 at addr ffff88802aa172c0 by task syz-executor413/5295 For bpf_prog_test_run_skb(), which uses a kmalloc()ed buffer passed to build_skb(). When build_skb() is passed a frag_size of 0, it means the buffer came from kmalloc. In these cases, ksize() is used to find its actual size, but since the allocation may not have been made to that size, actually perform the krealloc() call so that all the associated buffer size checking will be correctly notified. Split this logic out into a new interface, slab_build_skb(), but leave the original 0 checking for now to catch any stragglers. Reported-by: syzbot+fda18eaa8c12534ccb3b@syzkaller.appspotmail.com Link: https://groups.google.com/g/syzkaller-bugs/c/UnIKxTtU5-0/m/-wbXinkgAQ= AJ Fixes: 38931d8989b5 ("mm: Make ksize() a reporting-only function") Cc: Jakub Kicinski Cc: Eric Dumazet Cc: "David S. Miller" Cc: Paolo Abeni Cc: Pavel Begunkov Cc: pepsipu Cc: syzbot+fda18eaa8c12534ccb3b@syzkaller.appspotmail.com Cc: Vlastimil Babka Cc: kasan-dev Cc: Andrii Nakryiko Cc: ast@kernel.org Cc: bpf Cc: Daniel Borkmann Cc: Hao Luo Cc: Jesper Dangaard Brouer Cc: John Fastabend Cc: jolsa@kernel.org Cc: KP Singh Cc: martin.lau@linux.dev Cc: Stanislav Fomichev Cc: song@kernel.org Cc: Yonghong Song Cc: netdev@vger.kernel.org Cc: LKML Signed-off-by: Kees Cook --- Is this what you had in mind for this kind of change? v2: introduce separate helper (kuba) v1: https://lore.kernel.org/netdev/20221206231659.never.929-kees@kernel.org/ --- drivers/net/ethernet/broadcom/bnx2.c | 2 +- drivers/net/ethernet/qlogic/qed/qed_ll2.c | 2 +- include/linux/skbuff.h | 1 + net/bpf/test_run.c | 2 +- net/core/skbuff.c | 52 +++++++++++++++++++++-- 5 files changed, 52 insertions(+), 7 deletions(-) diff --git a/drivers/net/ethernet/broadcom/bnx2.c b/drivers/net/ethernet/br= oadcom/bnx2.c index fec57f1982c8..b2230a4a2086 100644 --- a/drivers/net/ethernet/broadcom/bnx2.c +++ b/drivers/net/ethernet/broadcom/bnx2.c @@ -3045,7 +3045,7 @@ bnx2_rx_skb(struct bnx2 *bp, struct bnx2_rx_ring_info= *rxr, u8 *data, =20 dma_unmap_single(&bp->pdev->dev, dma_addr, bp->rx_buf_use_size, DMA_FROM_DEVICE); - skb =3D build_skb(data, 0); + skb =3D slab_build_skb(data); if (!skb) { kfree(data); goto error; diff --git a/drivers/net/ethernet/qlogic/qed/qed_ll2.c b/drivers/net/ethern= et/qlogic/qed/qed_ll2.c index ed274f033626..e5116a86cfbc 100644 --- a/drivers/net/ethernet/qlogic/qed/qed_ll2.c +++ b/drivers/net/ethernet/qlogic/qed/qed_ll2.c @@ -200,7 +200,7 @@ static void qed_ll2b_complete_rx_packet(void *cxt, dma_unmap_single(&cdev->pdev->dev, buffer->phys_addr, cdev->ll2->rx_size, DMA_FROM_DEVICE); =20 - skb =3D build_skb(buffer->data, 0); + skb =3D slab_build_skb(buffer->data); if (!skb) { DP_INFO(cdev, "Failed to build SKB\n"); kfree(buffer->data); diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index 7be5bb4c94b6..0b391b635430 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -1253,6 +1253,7 @@ struct sk_buff *build_skb_around(struct sk_buff *skb, void skb_attempt_defer_free(struct sk_buff *skb); =20 struct sk_buff *napi_build_skb(void *data, unsigned int frag_size); +struct sk_buff *slab_build_skb(void *data); =20 /** * alloc_skb - allocate a network buffer diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c index 13d578ce2a09..611b1f4082cf 100644 --- a/net/bpf/test_run.c +++ b/net/bpf/test_run.c @@ -1130,7 +1130,7 @@ int bpf_prog_test_run_skb(struct bpf_prog *prog, cons= t union bpf_attr *kattr, } sock_init_data(NULL, sk); =20 - skb =3D build_skb(data, 0); + skb =3D slab_build_skb(data); if (!skb) { kfree(data); kfree(ctx); diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 1d9719e72f9d..2bff6af6a777 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -269,12 +269,10 @@ static struct sk_buff *napi_skb_cache_get(void) return skb; } =20 -/* Caller must provide SKB that is memset cleared */ -static void __build_skb_around(struct sk_buff *skb, void *data, - unsigned int frag_size) +static inline void __finalize_skb_around(struct sk_buff *skb, void *data, + unsigned int size) { struct skb_shared_info *shinfo; - unsigned int size =3D frag_size ? : ksize(data); =20 size -=3D SKB_DATA_ALIGN(sizeof(struct skb_shared_info)); =20 @@ -296,6 +294,52 @@ static void __build_skb_around(struct sk_buff *skb, vo= id *data, skb_set_kcov_handle(skb, kcov_common_handle()); } =20 +static inline void __slab_build_skb(struct sk_buff *skb, void *data, + unsigned int *size) +{ + void *resized; + + *size =3D ksize(data); + /* krealloc() will immediate return "data" when + * "ksize(data)" is requested: it is the existing upper + * bounds. As a result, GFP_ATOMIC will be ignored. + */ + resized =3D krealloc(data, *size, GFP_ATOMIC); + WARN_ON_ONCE(resized !=3D data); +} + +struct sk_buff *slab_build_skb(void *data) +{ + struct sk_buff *skb; + unsigned int size; + + skb =3D kmem_cache_alloc(skbuff_head_cache, GFP_ATOMIC); + if (unlikely(!skb)) + return NULL; + + memset(skb, 0, offsetof(struct sk_buff, tail)); + __slab_build_skb(skb, data, &size); + __finalize_skb_around(skb, data, size); + + return skb; +} +EXPORT_SYMBOL(slab_build_skb); + +/* Caller must provide SKB that is memset cleared */ +static void __build_skb_around(struct sk_buff *skb, void *data, + unsigned int frag_size) +{ + unsigned int size =3D frag_size; + + /* When frag_size =3D=3D 0, the buffer came from kmalloc, so we + * must find its true allocation size (and grow it to match). + */ + if (WARN_ONCE(size =3D=3D 0, "Use slab_build_skb() instead")) + __slab_build_skb(skb, data, &size); + + __finalize_skb_around(skb, data, size); +} + /** * __build_skb - build a network buffer * @data: data buffer provided by caller --=20 2.34.1