diff options
| author | Vlastimil Babka <vbabka@suse.cz> | 2021-08-20 16:17:27 +1000 |
|---|---|---|
| committer | Stephen Rothwell <sfr@canb.auug.org.au> | 2021-08-20 16:17:27 +1000 |
| commit | 10c9a9b135c1dfc6a110d503b68c4e0ba8f4ca26 (patch) | |
| tree | f27849a63570f3d459e4c557c302568fbbdc739b | |
| parent | 07dd9661b6f1dec344df7ea0b2abf5db9fc4a7c2 (diff) | |
| download | linux-next-10c9a9b135c1dfc6a110d503b68c4e0ba8f4ca26.tar.gz | |
mm, slub: prevent VM_BUG_ON in PageSlabPfmemalloc from ___slab_alloc
Notice: this object is not reachable from any branch.
Clark Williams reported [1] a VM_BUG_ON in PageSlabPfmemalloc:
page:000000009ac5dd73 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1ab3db
flags: 0x17ffffc0000000(node=0|zone=2|lastcpupid=0x1fffff)
raw: 0017ffffc0000000 ffffee1286aceb88 ffffee1287b66288 0000000000000000
raw: 0000000000000000 0000000000100000 00000000ffffffff 0000000000000000
page dumped because: VM_BUG_ON_PAGE(!PageSlab(page))
------------[ cut here ]------------
kernel BUG at include/linux/page-flags.h:814!
invalid opcode: 0000 [#1] PREEMPT_RT SMP PTI
CPU: 3 PID: 12345 Comm: hackbench Not tainted 5.14.0-rc5-rt8+ #12
Hardware name: /NUC5i7RYB, BIOS RYBDWi35.86A.0359.2016.0906.1028 09/06/2016
RIP: 0010:___slab_alloc+0x340/0x940
Code: c6 48 0f a3 05 b1 7b 57 03 72 99 c7 85 78 ff ff ff ff ff ff ff 48 8b 7d 88 e9 8d fd ff ff 48 c7 c6 50 5a 7c b0 e>
RSP: 0018:ffffba1c4a8b7ab0 EFLAGS: 00010293
RAX: 0000000000000000 RBX: 0000000000000002 RCX: ffff9bb765118000
RDX: 0000000000000000 RSI: ffffffffaf426050 RDI: 00000000ffffffff
RBP: ffffba1c4a8b7b70 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff9bb7410d3600
R13: 0000000000400cc0 R14: 00000000001f7770 R15: ffff9bbe76df7770
FS: 00007f474b1be740(0000) GS:ffff9bbe76c00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f60c04bdaf8 CR3: 0000000124f3a003 CR4: 00000000003706e0
Call Trace:
? __alloc_skb+0x1db/0x270
? __alloc_skb+0x1db/0x270
? kmem_cache_alloc_node+0xa4/0x2b0
kmem_cache_alloc_node+0xa4/0x2b0
__alloc_skb+0x1db/0x270
alloc_skb_with_frags+0x64/0x250
sock_alloc_send_pskb+0x260/0x2b0
? bpf_lsm_socket_getpeersec_dgram+0xa/0x10
unix_stream_sendmsg+0x27c/0x550
? unix_seqpacket_recvmsg+0x60/0x60
sock_sendmsg+0xbd/0xd0
sock_write_iter+0xb9/0x120
new_sync_write+0x175/0x200
vfs_write+0x3c4/0x510
ksys_write+0xc9/0x110
do_syscall_64+0x3b/0x90
entry_SYSCALL_64_after_hwframe+0x44/0xae
The problem is that we are opportunistically checking flags on a page in
irq enabled section. If we are interrupted and the page is freed, it's
not an issue as we detect it after disabling irqs. But on kernels with
CONFIG_DEBUG_VM. The check for PageSlab flag in PageSlabPfmemalloc() can
fail.
Fix this by creating an "unsafe" version of the check that doesn't check
PageSlab.
[1] https://lore.kernel.org/lkml/20210812151803.52f84aaf@theseus.lan/
Link: https://lkml.kernel.org/r/f4756ee5-a7e9-ab02-3aba-1355f77b7c79@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reported-by: Clark Williams <williams@redhat.com>
Tested-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Notice: this object is not reachable from any branch.
| -rw-r--r-- | include/linux/page-flags.h | 9 | ||||
| -rw-r--r-- | mm/slub.c | 15 |
2 files changed, 23 insertions, 1 deletions
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index 5922031ffab6e..7fda4fb85bdca 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -815,6 +815,15 @@ static inline int PageSlabPfmemalloc(struct page *page) return PageActive(page); } +/* + * A version of PageSlabPfmemalloc() for opportunistic checks where the page + * might have been freed under us and not be a PageSlab anymore. + */ +static inline int __PageSlabPfmemalloc(struct page *page) +{ + return PageActive(page); +} + static inline void SetPageSlabPfmemalloc(struct page *page) { VM_BUG_ON_PAGE(!PageSlab(page), page); diff --git a/mm/slub.c b/mm/slub.c index d1d39135d9f99..38458e3478103 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -2607,6 +2607,19 @@ static inline bool pfmemalloc_match(struct page *page, gfp_t gfpflags) } /* + * A variant of pfmemalloc_match() that tests page flags without asserting + * PageSlab. Intended for opportunistic checks before taking a lock and + * rechecking that nobody else freed the page under us. + */ +static inline bool pfmemalloc_match_unsafe(struct page *page, gfp_t gfpflags) +{ + if (unlikely(__PageSlabPfmemalloc(page))) + return gfp_pfmemalloc_allowed(gfpflags); + + return true; +} + +/* * Check the page->freelist of a page and either transfer the freelist to the * per cpu freelist or deactivate the page. * @@ -2707,7 +2720,7 @@ redo: * PFMEMALLOC but right now, we are losing the pfmemalloc * information when the page leaves the per-cpu allocator */ - if (unlikely(!pfmemalloc_match(page, gfpflags))) + if (unlikely(!try_pfmemalloc_match(page, gfpflags))) goto deactivate_slab; /* must check again c->page in case IRQ handler changed it */ |