This is a note to let you know that I've just added the patch titled erofs: fix partially uninitialized misuse in z_erofs_onlinepage_fixup to the 5.4-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: erofs-fix-partially-uninitialized-misuse-in-z_erofs_onlinepage_fixup.patch and it can be found in the queue-5.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 3c597282887fd55181578996dca52ce697d985a5 Mon Sep 17 00:00:00 2001 From: Gao Xiang <hsiangkao@xxxxxxxxxx> Date: Fri, 19 Jun 2020 07:43:49 +0800 Subject: erofs: fix partially uninitialized misuse in z_erofs_onlinepage_fixup From: Gao Xiang <hsiangkao@xxxxxxxxxx> commit 3c597282887fd55181578996dca52ce697d985a5 upstream. Hongyu reported "id != index" in z_erofs_onlinepage_fixup() with specific aarch64 environment easily, which wasn't shown before. After digging into that, I found that high 32 bits of page->private was set to 0xaaaaaaaa rather than 0 (due to z_erofs_onlinepage_init behavior with specific compiler options). Actually we only use low 32 bits to keep the page information since page->private is only 4 bytes on most 32-bit platforms. However z_erofs_onlinepage_fixup() uses the upper 32 bits by mistake. Let's fix it now. Reported-and-tested-by: Hongyu Jin <hongyu.jin@xxxxxxxxxx> Fixes: 3883a79abd02 ("staging: erofs: introduce VLE decompression support") Cc: <stable@xxxxxxxxxxxxxxx> # 4.19+ Reviewed-by: Chao Yu <yuchao0@xxxxxxxxxx> Link: https://lore.kernel.org/r/20200618234349.22553-1-hsiangkao@xxxxxxx Signed-off-by: Gao Xiang <hsiangkao@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- fs/erofs/zdata.h | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-) --- a/fs/erofs/zdata.h +++ b/fs/erofs/zdata.h @@ -148,22 +148,22 @@ static inline void z_erofs_onlinepage_in 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; } Patches currently in stable-queue which might be from hsiangkao@xxxxxxxxxx are queue-5.4/erofs-fix-partially-uninitialized-misuse-in-z_erofs_onlinepage_fixup.patch