From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Subject: uprobes: split THPs before trying to replace them
Patch series "Fix few rmap-related THP bugs", v3.
The patchset fixes handing PTE-mapped THPs in page_referenced() and
page_idle_clear_pte_refs().
To achieve that I've intrdocued new helper -- page_vma_mapped_walk() --
which replaces all page_check_address{,_transhuge}() and covers all THP
cases.
Patchset overview:
- First patch fixes one uprobe bug (unrelated to the rest of the
patchset, just spotted it at the same time);
- Patches 2-5 fix handling PTE-mapped THPs in page_referenced(),
page_idle_clear_pte_refs() and rmap core;
- Patches 6-12 convert all page_check_address{,_transhuge}() users (plus
remove_migration_pte()) to page_vma_mapped_walk() and drop unused helpers.
I think the fixes are not critical enough for stable@ as they don't lead
to crashes or hangs, only suboptimal behaviour.
This patch (of 12):
For THPs page_check_address() always fails. It leads to endless loop in
uprobe_write_opcode().
Testcase with huge-tmpfs (uprobes cannot probe anonymous memory).
mount -t debugfs none /sys/kernel/debug
mount -t tmpfs -o huge=always none /mnt
gcc -Wall -O2 -o /mnt/test -x c - <<EOF
int main(void)
{
return 0;
}
/* Padding to map the code segment with huge pmd */
asm (".zero 2097152");
EOF
echo 'p /mnt/test:0' > /sys/kernel/debug/tracing/uprobe_events
echo 1 > /sys/kernel/debug/tracing/events/uprobes/enable
/mnt/test
Let's split THPs before trying to replace.
Link: http://lkml.kernel.org/r/20170129173858.45174-2-kirill.shutemov@xxxxxxxxxxxxxxx
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Acked-by: Rik van Riel <riel@xxxxxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Hillf Danton <hillf.zj@xxxxxxxxxxxxxxx>
Cc: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>
Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/events/uprobes.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff -puN kernel/events/uprobes.c~uprobes-split-thps-before-trying-replace-them kernel/events/uprobes.c
--- a/kernel/events/uprobes.c~uprobes-split-thps-before-trying-replace-them
+++ a/kernel/events/uprobes.c
@@ -300,8 +300,8 @@ int uprobe_write_opcode(struct mm_struct
retry:
/* Read the page with vaddr into memory */
- ret = get_user_pages_remote(NULL, mm, vaddr, 1, FOLL_FORCE, &old_page,
- &vma, NULL);
+ ret = get_user_pages_remote(NULL, mm, vaddr, 1,
+ FOLL_FORCE | FOLL_SPLIT, &old_page, &vma, NULL);
if (ret <= 0)
return ret;
_
--
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