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| author | Matthew Wilcox (Oracle) <willy@infradead.org> | 2022-03-29 01:25:11 +0200 |
|---|---|---|
| committer | Matthew Wilcox (Oracle) <willy@infradead.org> | 2022-03-29 01:25:11 +0200 |
| commit | 3e3c658055c002900982513e289398a1aad4a488 (patch) | |
| tree | 53911e5e6154d643cfc9eb5cd7f375470ea61831 /lib/xarray.c | |
| parent | XArray: Include bitmap.h from xarray.h (diff) | |
| download | linux-3e3c658055c002900982513e289398a1aad4a488.tar.xz linux-3e3c658055c002900982513e289398a1aad4a488.zip | |
XArray: Fix xas_create_range() when multi-order entry present
If there is already an entry present that is of order >= XA_CHUNK_SHIFT
when we call xas_create_range(), xas_create_range() will misinterpret
that entry as a node and dereference xa_node->parent, generally leading
to a crash that looks something like this:
general protection fault, probably for non-canonical address 0xdffffc0000000001:
0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
CPU: 0 PID: 32 Comm: khugepaged Not tainted 5.17.0-rc8-syzkaller-00003-g56e337f2cf13 #0
RIP: 0010:xa_parent_locked include/linux/xarray.h:1207 [inline]
RIP: 0010:xas_create_range+0x2d9/0x6e0 lib/xarray.c:725
It's deterministically reproducable once you know what the problem is,
but producing it in a live kernel requires khugepaged to hit a race.
While the problem has been present since xas_create_range() was
introduced, I'm not aware of a way to hit it before the page cache was
converted to use multi-index entries.
Fixes: 6b24ca4a1a8d ("mm: Use multi-index entries in the page cache")
Reported-by: syzbot+0d2b0bf32ca5cfd09f2e@syzkaller.appspotmail.com
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Diffstat (limited to 'lib/xarray.c')
| -rw-r--r-- | lib/xarray.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/lib/xarray.c b/lib/xarray.c index 6f47f6375808..757644617b9b 100644 --- a/lib/xarray.c +++ b/lib/xarray.c @@ -722,6 +722,8 @@ void xas_create_range(struct xa_state *xas) for (;;) { struct xa_node *node = xas->xa_node; + if (node->shift >= shift) + break; xas->xa_node = xa_parent_locked(xas->xa, node); xas->xa_offset = node->offset - 1; if (node->offset != 0) |