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| author | Hugh Dickins <hughd@google.com> | 2014-01-12 01:25:21 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2014-01-12 16:47:15 +0700 |
| commit | eecc1e426d681351a6026a7d3e7d225f38955b6c (patch) | |
| tree | 894a98e88ffe18471b0c52eede6e119655d9fd09 /security | |
| parent | 518d00b7498c5894be94545848d55e5b9c55749e (diff) | |
| download | linux-eecc1e426d681351a6026a7d3e7d225f38955b6c.tar.bz2 | |
thp: fix copy_page_rep GPF by testing is_huge_zero_pmd once only
We see General Protection Fault on RSI in copy_page_rep: that RSI is
what you get from a NULL struct page pointer.
RIP: 0010:[<ffffffff81154955>] [<ffffffff81154955>] copy_page_rep+0x5/0x10
RSP: 0000:ffff880136e15c00 EFLAGS: 00010286
RAX: ffff880000000000 RBX: ffff880136e14000 RCX: 0000000000000200
RDX: 6db6db6db6db6db7 RSI: db73880000000000 RDI: ffff880dd0c00000
RBP: ffff880136e15c18 R08: 0000000000000200 R09: 000000000005987c
R10: 000000000005987c R11: 0000000000000200 R12: 0000000000000001
R13: ffffea00305aa000 R14: 0000000000000000 R15: 0000000000000000
FS: 00007f195752f700(0000) GS:ffff880c7fc20000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000093010000 CR3: 00000001458e1000 CR4: 00000000000027e0
Call Trace:
copy_user_huge_page+0x93/0xab
do_huge_pmd_wp_page+0x710/0x815
handle_mm_fault+0x15d8/0x1d70
__do_page_fault+0x14d/0x840
do_page_fault+0x2f/0x90
page_fault+0x22/0x30
do_huge_pmd_wp_page() tests is_huge_zero_pmd(orig_pmd) four times: but
since shrink_huge_zero_page() can free the huge_zero_page, and we have
no hold of our own on it here (except where the fourth test holds
page_table_lock and has checked pmd_same), it's possible for it to
answer yes the first time, but no to the second or third test. Change
all those last three to tests for NULL page.
(Note: this is not the same issue as trinity's DEBUG_PAGEALLOC BUG
in copy_page_rep with RSI: ffff88009c422000, reported by Sasha Levin
in https://lkml.org/lkml/2013/3/29/103. I believe that one is due
to the source page being split, and a tail page freed, while copy
is in progress; and not a problem without DEBUG_PAGEALLOC, since
the pmd_same check will prevent a miscopy from being made visible.)
Fixes: 97ae17497e99 ("thp: implement refcounting for huge zero page")
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: stable@vger.kernel.org # v3.10 v3.11 v3.12
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'security')
0 files changed, 0 insertions, 0 deletions