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Following crash occurs in validate_xmit_skb_list() when same skb is iterated multiple times in the loop and consume_skb() is called. The root cause is calling list_del_init(&skb->list) and not clearing skb->next in d4546c2509b1. list_del_init(&skb->list) sets skb->next to point to skb itself. skb->next needs to be cleared because other parts of network stack uses another kind of SKB lists. validate_xmit_skb_list() uses such list. A similar type of bugfix was reported by Jesper Dangaard Brouer. https://patchwork.ozlabs.org/patch/942541/ This patch clears skb->next and changes list_del_init() to list_del() so that list->prev will maintain the list poison. [ 148.185511] ================================================================== [ 148.187865] BUG: KASAN: use-after-free in validate_xmit_skb_list+0x4b/0xa0 [ 148.190158] Read of size 8 at addr ffff8801e52eefc0 by task swapper/1/0 [ 148.192940] [ 148.193642] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.18.0-rc3+ #25 [ 148.195423] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-20180531_142017-buildhw-08.phx2.fedoraproject.org-1.fc28 04/01/2014 [ 148.199129] Call Trace: [ 148.200565] <IRQ> [ 148.201911] dump_stack+0xc6/0x14c [ 148.203572] ? dump_stack_print_info.cold.1+0x2f/0x2f [ 148.205083] ? kmsg_dump_rewind_nolock+0x59/0x59 [ 148.206307] ? validate_xmit_skb+0x2c6/0x560 [ 148.207432] ? debug_show_held_locks+0x30/0x30 [ 148.208571] ? validate_xmit_skb_list+0x4b/0xa0 [ 148.211144] print_address_description+0x6c/0x23c [ 148.212601] ? validate_xmit_skb_list+0x4b/0xa0 [ 148.213782] kasan_report.cold.6+0x241/0x2fd [ 148.214958] validate_xmit_skb_list+0x4b/0xa0 [ 148.216494] sch_direct_xmit+0x1b0/0x680 [ 148.217601] ? dev_watchdog+0x4e0/0x4e0 [ 148.218675] ? do_raw_spin_trylock+0x10/0x120 [ 148.219818] ? do_raw_spin_lock+0xe0/0xe0 [ 148.221032] __dev_queue_xmit+0x1167/0x1810 [ 148.222155] ? sched_clock+0x5/0x10 [...] [ 148.474257] Allocated by task 0: [ 148.475363] kasan_kmalloc+0xbf/0xe0 [ 148.476503] kmem_cache_alloc+0xb4/0x1b0 [ 148.477654] __build_skb+0x91/0x250 [ 148.478677] build_skb+0x67/0x180 [ 148.479657] e1000_clean_rx_irq+0x542/0x8a0 [ 148.480757] e1000_clean+0x652/0xd10 [ 148.481772] net_rx_action+0x4ea/0xc20 [ 148.482808] __do_softirq+0x1f9/0x574 [ 148.483831] [ 148.484575] Freed by task 0: [ 148.485504] __kasan_slab_free+0x12e/0x180 [ 148.486589] kmem_cache_free+0xb4/0x240 [ 148.487634] kfree_skbmem+0xed/0x150 [ 148.488648] consume_skb+0x146/0x250 [ 148.489665] validate_xmit_skb+0x2b7/0x560 [ 148.490754] validate_xmit_skb_list+0x70/0xa0 [ 148.491897] sch_direct_xmit+0x1b0/0x680 [ 148.493949] __dev_queue_xmit+0x1167/0x1810 [ 148.495103] br_dev_queue_push_xmit+0xce/0x250 [ 148.496196] br_forward_finish+0x276/0x280 [ 148.497234] __br_forward+0x44f/0x520 [ 148.498260] br_forward+0x19f/0x1b0 [ 148.499264] br_handle_frame_finish+0x65e/0x980 [ 148.500398] NF_HOOK.constprop.10+0x290/0x2a0 [ 148.501522] br_handle_frame+0x417/0x640 [ 148.502582] __netif_receive_skb_core+0xaac/0x18f0 [ 148.503753] __netif_receive_skb_one_core+0x98/0x120 [ 148.504958] netif_receive_skb_internal+0xe3/0x330 [ 148.506154] napi_gro_complete+0x190/0x2a0 [ 148.507243] dev_gro_receive+0x9f7/0x1100 [ 148.508316] napi_gro_receive+0xcb/0x260 [ 148.509387] e1000_clean_rx_irq+0x2fc/0x8a0 [ 148.510501] e1000_clean+0x652/0xd10 [ 148.511523] net_rx_action+0x4ea/0xc20 [ 148.512566] __do_softirq+0x1f9/0x574 [ 148.513598] [ 148.514346] The buggy address belongs to the object at ffff8801e52eefc0 [ 148.514346] which belongs to the cache skbuff_head_cache of size 232 [ 148.517047] The buggy address is located 0 bytes inside of [ 148.517047] 232-byte region [ffff8801e52eefc0, ffff8801e52ef0a8) [ 148.519549] The buggy address belongs to the page: [ 148.520726] page:ffffea000794bb00 count:1 mapcount:0 mapping:ffff880106f4dfc0 index:0xffff8801e52ee840 compound_mapcount: 0 [ 148.524325] flags: 0x17ffffc0008100(slab|head) [ 148.525481] raw: 0017ffffc0008100 ffff880106b938d0 ffff880106b938d0 ffff880106f4dfc0 [ 148.527503] raw: ffff8801e52ee840 0000000000190011 00000001ffffffff 0000000000000000 [ 148.529547] page dumped because: kasan: bad access detected Fixes: d4546c2509b1 ("net: Convert GRO SKB handling to list_head.") Signed-off-by: Prashant Bhole <bhole_prashant_q7@lab.ntt.co.jp> Reported-by: Tyler Hicks <tyhicks@canonical.com> Tested-by: Tyler Hicks <tyhicks@canonical.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.