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Bug 1660826 - Work around apparent bug with sendmsg() in some 64-bit Android devices. r=nika

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Some Android ARM64 devices appear to have a bug where sendmsg sometimes
returns 0xFFFFFFFF, which we're assuming is a -1 that was incorrectly
truncated to 32-bit and then zero-extended.  This patch detects that
value (which should never legitimately be returned, because it's 16x
the maximum message size) and replaces it with -1, with some additional
assertions.

The workaround is also enabled on x86_64 Android on debug builds only,
so that the code has CI coverage.

Differential Revision: https://phabricator.services.mozilla.com/D89845
This commit is contained in:
Jed Davis 2020-09-11 04:31:50 +00:00
parent c4dd52a672
commit c0cd7e11b5
1 changed files with 38 additions and 1 deletions
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39
ipc/chromium/src/chrome/common/ipc_channel_posix.cc
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@ -108,6 +108,42 @@ bool SetCloseOnExec(int fd) {
bool ErrorIsBrokenPipe(int err) { return err == EPIPE || err == ECONNRESET; }
// Some Android ARM64 devices appear to have a bug where sendmsg
// sometimes returns 0xFFFFFFFF, which we're assuming is a -1 that was
// incorrectly truncated to 32-bit and then zero-extended.
// See bug 1660826 for details.
//
// This is a workaround to detect that value and replace it with -1
// (and check that there really was an error), because the largest
// amount we'll ever write is Channel::kMaximumMessageSize (256MiB).
//
// The workaround is also enabled on x86_64 Android on debug builds,
// although the bug isn't known to manifest there, so that there will
// be some CI coverage of this code.
static inline ssize_t corrected_sendmsg(int socket,
const struct msghdr* message,
int flags) {
#if defined(ANDROID) && \
(defined(__aarch64__) || (defined(DEBUG) && defined(__x86_64__)))
static constexpr auto kBadValue = static_cast<ssize_t>(0xFFFFFFFF);
static_assert(kBadValue > 0);
# ifdef MOZ_DIAGNOSTIC_ASSERT_ENABLED
errno = 0;
# endif
ssize_t bytes_written = sendmsg(socket, message, flags);
if (bytes_written == kBadValue) {
MOZ_DIAGNOSTIC_ASSERT(errno != 0);
bytes_written = -1;
}
MOZ_DIAGNOSTIC_ASSERT(bytes_written < kBadValue);
return bytes_written;
#else
return sendmsg(socket, message, flags);
#endif
}
} // namespace
//------------------------------------------------------------------------------
@ -616,7 +652,8 @@ bool Channel::ChannelImpl::ProcessOutgoingMessages() {
msgh.msg_iov = iov;
msgh.msg_iovlen = iov_count;
ssize_t bytes_written = HANDLE_EINTR(sendmsg(pipe_, &msgh, MSG_DONTWAIT));
ssize_t bytes_written =
HANDLE_EINTR(corrected_sendmsg(pipe_, &msgh, MSG_DONTWAIT));
#if !defined(OS_MACOSX)
// On OSX CommitAll gets called later, once we get the