From: Paolo Abeni pabeni@redhat.com

[ Upstream commit 14ad6ed30a10afbe91b0749d6378285f4225d482 ]

Sabrina reported the following splat:

WARNING: CPU: 0 PID: 1 at net/core/dev.c:6935 netif_napi_add_weight_locked+0x8f2/0xba0 Modules linked in: CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.14.0-rc1-net-00092-g011b03359038 #996 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Arch Linux 1.16.3-1-1 04/01/2014 RIP: 0010:netif_napi_add_weight_locked+0x8f2/0xba0 Code: e8 c3 e6 6a fe 48 83 c4 28 5b 5d 41 5c 41 5d 41 5e 41 5f c3 cc cc cc cc c7 44 24 10 ff ff ff ff e9 8f fb ff ff e8 9e e6 6a fe <0f> 0b e9 d3 fe ff ff e8 92 e6 6a fe 48 8b 04 24 be ff ff ff ff 48 RSP: 0000:ffffc9000001fc60 EFLAGS: 00010293 RAX: 0000000000000000 RBX: ffff88806ce48128 RCX: 1ffff11001664b9e RDX: ffff888008f00040 RSI: ffffffff8317ca42 RDI: ffff88800b325cb6 RBP: ffff88800b325c40 R08: 0000000000000001 R09: ffffed100167502c R10: ffff88800b3a8163 R11: 0000000000000000 R12: ffff88800ac1c168 R13: ffff88800ac1c168 R14: ffff88800ac1c168 R15: 0000000000000007 FS: 0000000000000000(0000) GS:ffff88806ce00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffff888008201000 CR3: 0000000004c94001 CR4: 0000000000370ef0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> gro_cells_init+0x1ba/0x270 xfrm_input_init+0x4b/0x2a0 xfrm_init+0x38/0x50 ip_rt_init+0x2d7/0x350 ip_init+0xf/0x20 inet_init+0x406/0x590 do_one_initcall+0x9d/0x2e0 do_initcalls+0x23b/0x280 kernel_init_freeable+0x445/0x490 kernel_init+0x20/0x1d0 ret_from_fork+0x46/0x80 ret_from_fork_asm+0x1a/0x30 </TASK> irq event stamp: 584330 hardirqs last enabled at (584338): [<ffffffff8168bf87>] __up_console_sem+0x77/0xb0 hardirqs last disabled at (584345): [<ffffffff8168bf6c>] __up_console_sem+0x5c/0xb0 softirqs last enabled at (583242): [<ffffffff833ee96d>] netlink_insert+0x14d/0x470 softirqs last disabled at (583754): [<ffffffff8317c8cd>] netif_napi_add_weight_locked+0x77d/0xba0

on kernel built with MAX_SKB_FRAGS=45, where SKB_WITH_OVERHEAD(1024) is smaller than GRO_MAX_HEAD.

Such built additionally contains the revert of the single page frag cache so that napi_get_frags() ends up using the page frag allocator, triggering the splat.

Note that the underlying issue is independent from the mentioned revert; address it ensuring that the small head cache will fit either TCP and GRO allocation and updating napi_alloc_skb() and __netdev_alloc_skb() to select kmalloc() usage for any allocation fitting such cache.

Reported-by: Sabrina Dubroca sd@queasysnail.net Suggested-by: Eric Dumazet edumazet@google.com Fixes: 3948b05950fd ("net: introduce a config option to tweak MAX_SKB_FRAGS") Reviewed-by: Eric Dumazet edumazet@google.com Signed-off-by: Paolo Abeni pabeni@redhat.com [ Minor context change fixed. ] Signed-off-by: Wenshan Lan jetlan9@163.com --- include/net/gro.h | 3 +++ net/core/gro.c | 3 --- net/core/skbuff.c | 10 +++++++--- 3 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/include/net/gro.h b/include/net/gro.h index 018343254c90..9260ed367c91 100644 --- a/include/net/gro.h +++ b/include/net/gro.h @@ -10,6 +10,9 @@ #include <linux/skbuff.h> #include <net/udp.h>

+/* This should be increased if a protocol with a bigger head is added. */ +#define GRO_MAX_HEAD (MAX_HEADER + 128) + struct napi_gro_cb { union { struct { diff --git a/net/core/gro.c b/net/core/gro.c index 397cf5984250..b8cc44406e69 100644 --- a/net/core/gro.c +++ b/net/core/gro.c @@ -6,9 +6,6 @@

#define MAX_GRO_SKBS 8

-/* This should be increased if a protocol with a bigger head is added. */ -#define GRO_MAX_HEAD (MAX_HEADER + 128) - static DEFINE_SPINLOCK(offload_lock); struct list_head offload_base __read_mostly = LIST_HEAD_INIT(offload_base); /* Maximum number of GRO_NORMAL skbs to batch up for list-RX */ diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 867832f8bbae..073e2c527407 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -67,6 +67,7 @@ #include <net/dst.h> #include <net/sock.h> #include <net/checksum.h> +#include <net/gro.h> #include <net/gso.h> #include <net/ip6_checksum.h> #include <net/xfrm.h> @@ -96,7 +97,9 @@ static struct kmem_cache *skbuff_ext_cache __ro_after_init;

static struct kmem_cache *skb_small_head_cache __ro_after_init;

-#define SKB_SMALL_HEAD_SIZE SKB_HEAD_ALIGN(MAX_TCP_HEADER) +#define GRO_MAX_HEAD_PAD (GRO_MAX_HEAD + NET_SKB_PAD + NET_IP_ALIGN) +#define SKB_SMALL_HEAD_SIZE SKB_HEAD_ALIGN(max(MAX_TCP_HEADER, \ + GRO_MAX_HEAD_PAD))

/* We want SKB_SMALL_HEAD_CACHE_SIZE to not be a power of two. * This should ensure that SKB_SMALL_HEAD_HEADROOM is a unique @@ -708,7 +711,7 @@ struct sk_buff *__netdev_alloc_skb(struct net_device *dev, unsigned int len, /* If requested length is either too small or too big, * we use kmalloc() for skb->head allocation. */ - if (len <= SKB_WITH_OVERHEAD(1024) || + if (len <= SKB_WITH_OVERHEAD(SKB_SMALL_HEAD_CACHE_SIZE) || len > SKB_WITH_OVERHEAD(PAGE_SIZE) || (gfp_mask & (__GFP_DIRECT_RECLAIM | GFP_DMA))) { skb = __alloc_skb(len, gfp_mask, SKB_ALLOC_RX, NUMA_NO_NODE); @@ -785,7 +788,8 @@ struct sk_buff *__napi_alloc_skb(struct napi_struct *napi, unsigned int len, * When the small frag allocator is available, prefer it over kmalloc * for small fragments */ - if ((!NAPI_HAS_SMALL_PAGE_FRAG && len <= SKB_WITH_OVERHEAD(1024)) || + if ((!NAPI_HAS_SMALL_PAGE_FRAG && + len <= SKB_WITH_OVERHEAD(SKB_SMALL_HEAD_CACHE_SIZE)) || len > SKB_WITH_OVERHEAD(PAGE_SIZE) || (gfp_mask & (__GFP_DIRECT_RECLAIM | GFP_DMA))) { skb = __alloc_skb(len, gfp_mask, SKB_ALLOC_RX | SKB_ALLOC_NAPI,