This is a note to let you know that I've just added the patch titled
mm: khugepaged: fix kernel BUG in hpage_collapse_scan_file()
to the 6.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mm-khugepaged-fix-kernel-bug-in-hpage_collapse_scan_.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 0f4e4d9e96e9773b2f9dd19979c9348680cf5902
Author: Ivan Orlov <ivan.orlov0322@xxxxxxxxx>
Date: Wed Mar 29 18:53:30 2023 +0400
mm: khugepaged: fix kernel BUG in hpage_collapse_scan_file()
[ Upstream commit 2ce0bdfebc74f6cbd4e97a4e767d505a81c38cf2 ]
Syzkaller reported the following issue:
kernel BUG at mm/khugepaged.c:1823!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 5097 Comm: syz-executor220 Not tainted 6.2.0-syzkaller-13154-g857f1268a591 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/16/2023
RIP: 0010:collapse_file mm/khugepaged.c:1823 [inline]
RIP: 0010:hpage_collapse_scan_file+0x67c8/0x7580 mm/khugepaged.c:2233
Code: 00 00 89 de e8 c9 66 a3 ff 31 ff 89 de e8 c0 66 a3 ff 45 84 f6 0f 85 28 0d 00 00 e8 22 64 a3 ff e9 dc f7 ff ff e8 18 64 a3 ff <0f> 0b f3 0f 1e fa e8 0d 64 a3 ff e9 93 f6 ff ff f3 0f 1e fa 4c 89
RSP: 0018:ffffc90003dff4e0 EFLAGS: 00010093
RAX: ffffffff81e95988 RBX: 00000000000001c1 RCX: ffff8880205b3a80
RDX: 0000000000000000 RSI: 00000000000001c0 RDI: 00000000000001c1
RBP: ffffc90003dff830 R08: ffffffff81e90e67 R09: fffffbfff1a433c3
R10: 0000000000000000 R11: dffffc0000000001 R12: 0000000000000000
R13: ffffc90003dff6c0 R14: 00000000000001c0 R15: 0000000000000000
FS: 00007fdbae5ee700(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fdbae6901e0 CR3: 000000007b2dd000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
madvise_collapse+0x721/0xf50 mm/khugepaged.c:2693
madvise_vma_behavior mm/madvise.c:1086 [inline]
madvise_walk_vmas mm/madvise.c:1260 [inline]
do_madvise+0x9e5/0x4680 mm/madvise.c:1439
__do_sys_madvise mm/madvise.c:1452 [inline]
__se_sys_madvise mm/madvise.c:1450 [inline]
__x64_sys_madvise+0xa5/0xb0 mm/madvise.c:1450
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
The xas_store() call during page cache scanning can potentially translate
'xas' into the error state (with the reproducer provided by the syzkaller
the error code is -ENOMEM). However, there are no further checks after
the 'xas_store', and the next call of 'xas_next' at the start of the
scanning cycle doesn't increase the xa_index, and the issue occurs.
This patch will add the xarray state error checking after the xas_store()
and the corresponding result error code.
Tested via syzbot.
[akpm@xxxxxxxxxxxxxxxxxxxx: update include/trace/events/huge_memory.h's SCAN_STATUS]
Link: https://lkml.kernel.org/r/20230329145330.23191-1-ivan.orlov0322@xxxxxxxxx
Link: https://syzkaller.appspot.com/bug?id=7d6bb3760e026ece7524500fe44fb024a0e959fc
Signed-off-by: Ivan Orlov <ivan.orlov0322@xxxxxxxxx>
Reported-by: syzbot+9578faa5475acb35fa50@xxxxxxxxxxxxxxxxxxxxxxxxx
Tested-by: Zach O'Keefe <zokeefe@xxxxxxxxxx>
Cc: Yang Shi <shy828301@xxxxxxxxx>
Cc: Himadri Pandya <himadrispandya@xxxxxxxxx>
Cc: Ivan Orlov <ivan.orlov0322@xxxxxxxxx>
Cc: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx>
Cc: Song Liu <songliubraving@xxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/include/trace/events/huge_memory.h b/include/trace/events/huge_memory.h
index 760455dfa8600..01591e7995235 100644
--- a/include/trace/events/huge_memory.h
+++ b/include/trace/events/huge_memory.h
@@ -36,7 +36,8 @@
EM( SCAN_ALLOC_HUGE_PAGE_FAIL, "alloc_huge_page_failed") \
EM( SCAN_CGROUP_CHARGE_FAIL, "ccgroup_charge_failed") \
EM( SCAN_TRUNCATED, "truncated") \
- EMe(SCAN_PAGE_HAS_PRIVATE, "page_has_private") \
+ EM( SCAN_PAGE_HAS_PRIVATE, "page_has_private") \
+ EMe(SCAN_STORE_FAILED, "store_failed")
#undef EM
#undef EMe
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 65bd0b105266a..085fca1fa27af 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -55,6 +55,7 @@ enum scan_result {
SCAN_CGROUP_CHARGE_FAIL,
SCAN_TRUNCATED,
SCAN_PAGE_HAS_PRIVATE,
+ SCAN_STORE_FAILED,
};
#define CREATE_TRACE_POINTS
@@ -1840,6 +1841,15 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
goto xa_locked;
}
xas_store(&xas, hpage);
+ if (xas_error(&xas)) {
+ /* revert shmem_charge performed
+ * in the previous condition
+ */
+ mapping->nrpages--;
+ shmem_uncharge(mapping->host, 1);
+ result = SCAN_STORE_FAILED;
+ goto xa_locked;
+ }
nr_none++;
continue;
}
@@ -1991,6 +2001,11 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
/* Finally, replace with the new page. */
xas_store(&xas, hpage);
+ /* We can't get an ENOMEM here (because the allocation happened before)
+ * but let's check for errors (XArray implementation can be
+ * changed in the future)
+ */
+ WARN_ON_ONCE(xas_error(&xas));
continue;
out_unlock:
unlock_page(page);
@@ -2028,6 +2043,11 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
/* Join all the small entries into a single multi-index entry */
xas_set_order(&xas, start, HPAGE_PMD_ORDER);
xas_store(&xas, hpage);
+ /* Here we can't get an ENOMEM (because entries were
+ * previously allocated) But let's check for errors
+ * (XArray implementation can be changed in the future)
+ */
+ WARN_ON_ONCE(xas_error(&xas));
xa_locked:
xas_unlock_irq(&xas);
xa_unlocked:
