The patch titled Subject: netvm: check for page == NULL when propagating the skb->pfmemalloc flag has been removed from the -mm tree. Its filename was netvm-check-for-page-==-null-when-propagating-the-skb-pfmemalloc-flag.patch This patch was dropped because an updated version will be merged ------------------------------------------------------ From: Mel Gorman <mgorman@xxxxxxx> Subject: netvm: check for page == NULL when propagating the skb->pfmemalloc flag Commit c48a11c7 ("netvm: propagate page->pfmemalloc to skb") is responsible for the following bug triggered by a xen network driver [ 1.908592] BUG: unable to handle kernel NULL pointer dereference at 0000000000000010 [ 1.908643] IP: [<ffffffffa0037750>] xennet_poll+0x980/0xec0 [xen_netfront] [ 1.908703] PGD ea1df067 PUD e8ada067 PMD 0 [ 1.908774] Oops: 0000 [#1] SMP [ 1.908797] Modules linked in: fbcon tileblit font radeon bitblit softcursor ttm drm_kms_helper crc32c_intel xen_blkfront xen_netfront xen_fbfront fb_sys_fops sysimgblt sysfillrect syscopyarea +xen_kbdfront xenfs xen_privcmd [ 1.908938] CPU 0 [ 1.908950] Pid: 2165, comm: ip Not tainted 3.5.0upstream-08854-g444fa66 #1 [ 1.908983] RIP: e030:[<ffffffffa0037750>] [<ffffffffa0037750>] xennet_poll+0x980/0xec0 [xen_netfront] [ 1.909029] RSP: e02b:ffff8800ffc03db8 EFLAGS: 00010282 [ 1.909055] RAX: ffff8800ea010140 RBX: ffff8800f00e86c0 RCX: 000000000000009a [ 1.909055] RDX: 0000000000000040 RSI: 000000000000005a RDI: ffff8800fa7dee80 [ 1.909055] RBP: ffff8800ffc03ee8 R08: ffff8800f00e86d8 R09: ffff8800ea010000 [ 1.909055] R10: dead000000200200 R11: dead000000100100 R12: ffff8800fa7dee80 [ 1.909055] R13: 000000000000005a R14: ffff8800fa7dee80 R15: 0000000000000200 [ 1.909055] FS: 00007fbafc188700(0000) GS:ffff8800ffc00000(0000) knlGS:0000000000000000 [ 1.909055] CS: e033 DS: 0000 ES: 0000 CR0: 000000008005003b [ 1.909055] CR2: 0000000000000010 CR3: 00000000ea108000 CR4: 0000000000002660 [ 1.909055] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 1.909055] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 [ 1.909055] Process ip (pid: 2165, threadinfo ffff8800ea0f2000, task ffff8800fa783040) [ 1.909055] Stack: [ 1.909055] ffff8800e27e5040 ffff8800ffc03e88 ffff8800ffc03e68 ffff8800ffc03e48 [ 1.909055] 7fffffffffffffff ffff8800ffc03e00 ffff8800e27e5040 ffff8800f00e86d8 [ 1.909055] ffff8800ffc03eb0 00000040ffffffff ffff8800f00e8000 00000000ffc03e30 [ 1.909055] Call Trace: [ 1.909055] <IRQ> [ 1.909055] [<ffffffff81066028>] ? pvclock_clocksource_read+0x58/0xd0 [ 1.909055] [<ffffffff81486352>] net_rx_action+0x112/0x240 [ 1.909055] [<ffffffff8107f319>] __do_softirq+0xb9/0x190 [ 1.909055] [<ffffffff815d8d7c>] call_softirq+0x1c/0x30 The problem is that the xenfront driver is passing a NULL page to __skb_fill_page_desc() which was unexpected. This patch checks that there is a page before dereferencing. Signed-off-by: Mel Gorman <mgorman@xxxxxxx> Reported-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> Tested-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> Cc: Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx> Cc: David Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/skbuff.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff -puN include/linux/skbuff.h~netvm-check-for-page-==-null-when-propagating-the-skb-pfmemalloc-flag include/linux/skbuff.h --- a/include/linux/skbuff.h~netvm-check-for-page-==-null-when-propagating-the-skb-pfmemalloc-flag +++ a/include/linux/skbuff.h @@ -1256,7 +1256,7 @@ static inline void __skb_fill_page_desc( * do not lose pfmemalloc information as the pages would not be * allocated using __GFP_MEMALLOC. */ - if (page->pfmemalloc && !page->mapping) + if (page && page->pfmemalloc && !page->mapping) skb->pfmemalloc = true; frag->page.p = page; frag->page_offset = off; _ Patches currently in -mm which might be from mgorman@xxxxxxx are origin.patch mm-correct-page-pfmemalloc-to-fix-deactivate_slab-regression.patch mm-have-order-0-compaction-start-near-a-pageblock-with-free-pages-v2.patch mm-compaction-abort-async-compaction-if-locks-are-contended-or-taking-too-long-v2.patch linux-next.patch mm-remove-__gfp_no_kswapd.patch mm-compaction-update-comment-in-try_to_compact_pages.patch mm-vmscan-scale-number-of-pages-reclaimed-by-reclaim-compaction-based-on-failures.patch mm-compaction-capture-a-suitable-high-order-page-immediately-when-it-is-made-available.patch revert-mm-mempolicy-let-vma_merge-and-vma_split-handle-vma-vm_policy-linkages.patch mempolicy-remove-mempolicy-sharing.patch mempolicy-fix-a-race-in-shared_policy_replace.patch mempolicy-fix-refcount-leak-in-mpol_set_shared_policy.patch mempolicy-fix-a-memory-corruption-by-refcount-imbalance-in-alloc_pages_vma.patch mempolicy-fix-a-memory-corruption-by-refcount-imbalance-in-alloc_pages_vma-v2.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html