[PATCH v2 0/1] MR4310: ntdll: Tweak the binary representation of SRWLOCK.
There are applications that uses SRWLOCK in an invalid way and then checks its binary representation. Specifically they releases an unlocked SRWLOCK then check its bit pattern is all-ones. Tweak the representation a bit so they are happy. -- v2: ntdll: Tweak the binary representation of SRWLOCK. https://gitlab.winehq.org/wine/wine/-/merge_requests/4310
From: Yuxuan Shui <yshui(a)codeweavers.com> There are applications that uses SRWLOCK in an invalid way and then checks its binary representation. Tweak our representation a bit so they are happy. --- dlls/ntdll/sync.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/dlls/ntdll/sync.c b/dlls/ntdll/sync.c index fa64917029a..90370abba09 100644 --- a/dlls/ntdll/sync.c +++ b/dlls/ntdll/sync.c @@ -473,8 +473,6 @@ DWORD WINAPI RtlRunOnceExecuteOnce( RTL_RUN_ONCE *once, PRTL_RUN_ONCE_INIT_FN fu struct srw_lock { - short exclusive_waiters; - /* Number of shared owners, or -1 if owned exclusive. * * Sadly Windows has no equivalent to FUTEX_WAIT_BITSET, so in order to wake @@ -487,6 +485,8 @@ struct srw_lock * must not be the first element in the structure. */ short owners; + + short exclusive_waiters; }; C_ASSERT( sizeof(struct srw_lock) == 4 ); -- GitLab https://gitlab.winehq.org/wine/wine/-/merge_requests/4310
After some experimentation, I believe WeCom is doing 2 tests. The "releasing an unlocked SRWLOCK and see if it's all-1s" only happens after the first test fails. Swapping the 2 fields is enough to pass the first test. -- https://gitlab.winehq.org/wine/wine/-/merge_requests/4310#note_51095
I didn't notice `owners` can't be the first field... Is there a way around that? -- https://gitlab.winehq.org/wine/wine/-/merge_requests/4310#note_51099
On Mon Nov 6 16:28:16 2023 +0000, Yuxuan Shui wrote:
I didn't notice `owners` can't be the first field... Is there a way around that? OK, I looked around a bit. `WaitOnAddress` has a size parameter, isn't that enough to indicate waiting on `owners` only? We don't need the non-four-byte-aligned-ness for that.
-- https://gitlab.winehq.org/wine/wine/-/merge_requests/4310#note_51100
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Yuxuan Shui (＠yshui)