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Fix a regression which uses potential uninitialized
 high 32-bit value unexpectedly recently observed with
 specific compiler options.
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Merge tag 'erofs-for-5.8-rc3-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs

Pull erofs fix from Gao Xiang:
 "Fix a regression which uses potential uninitialized high 32-bit value
  unexpectedly recently observed with specific compiler options"

* tag 'erofs-for-5.8-rc3-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs:
  erofs: fix partially uninitialized misuse in z_erofs_onlinepage_fixup
This commit is contained in:
Linus Torvalds 2020-06-24 17:39:30 -07:00
commit 8be3a53e18
1 changed files with 10 additions and 10 deletions
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20
fs/erofs/zdata.h
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@ -144,22 +144,22 @@ static inline void z_erofs_onlinepage_init(struct page *page)
static inline void z_erofs_onlinepage_fixup(struct page *page,
uintptr_t index, bool down)
{
unsigned long *p, o, v, id;
repeat:
p = &page_private(page);
o = READ_ONCE(*p);
union z_erofs_onlinepage_converter u = { .v = &page_private(page) };
int orig, orig_index, val;
id = o >> Z_EROFS_ONLINEPAGE_INDEX_SHIFT;
if (id) {
repeat:
orig = atomic_read(u.o);
orig_index = orig >> Z_EROFS_ONLINEPAGE_INDEX_SHIFT;
if (orig_index) {
if (!index)
return;
DBG_BUGON(id != index);
DBG_BUGON(orig_index != index);
}
v = (index << Z_EROFS_ONLINEPAGE_INDEX_SHIFT) |
((o & Z_EROFS_ONLINEPAGE_COUNT_MASK) + (unsigned int)down);
if (cmpxchg(p, o, v) != o)
val = (index << Z_EROFS_ONLINEPAGE_INDEX_SHIFT) |
((orig & Z_EROFS_ONLINEPAGE_COUNT_MASK) + (unsigned int)down);
if (atomic_cmpxchg(u.o, orig, val) != orig)
goto repeat;
}