[chromium linker] Check for null ParcelFileDescriptor before using it.

[chromium linker] Check for null ParcelFileDescriptor before using it.

When CreateSharedRelro fails, the file descriptor read by LibInfo from the parcel will be null, but
the child processes are trying to call its methods anyway. Added a check to avoid NPE.

BUG=409826
Committed: https://crrev.com/43fb252a05ebeb21097abb816d2ccea1ec84dbbc
Cr-Commit-Position: refs/heads/master@{#293164}

[nyquist, 2014-09-03 16:23:49]

nyquist@chromium.org changed reviewers:
+ nyquist@chromium.org

[nyquist, 2014-09-03 16:23:50]

lgtm

[whywhat, 2014-09-03 16:27:48]

The CQ bit was checked by avayvod@chromium.org

[commit-bot: I haz the power, 2014-09-03 16:31:11]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/avayvod@chromium.org/538543002/1

[simonb (inactive), 2014-09-03 16:32:37]

simonb@chromium.org changed reviewers:
+ simonb@chromium.org

[simonb (inactive), 2014-09-03 16:32:37]

lgtm

https://codereview.chromium.org/538543002/diff/1/base/android/java/src/org/ch...
File base/android/java/src/org/chromium/base/library_loader/Linker.java (right):

https://codereview.chromium.org/538543002/diff/1/base/android/java/src/org/ch...
base/android/java/src/org/chromium/base/library_loader/Linker.java:957: mRelroFd
= (fd == null) ? -1 : fd.detachFd();
Maybe reverse the condition so that the 'exception' case is last?

mRelroFd = (fd != null) ? fd.detachFd() : -1;

[whywhat, 2014-09-03 16:38:29]

Thanks for the reviews!

https://codereview.chromium.org/538543002/diff/1/base/android/java/src/org/ch...
File base/android/java/src/org/chromium/base/library_loader/Linker.java (right):

https://codereview.chromium.org/538543002/diff/1/base/android/java/src/org/ch...
base/android/java/src/org/chromium/base/library_loader/Linker.java:957: mRelroFd
= (fd == null) ? -1 : fd.detachFd();
On 2014/09/03 16:32:37, simonb wrote:
> Maybe reverse the condition so that the 'exception' case is last?
> 
> mRelroFd = (fd != null) ? fd.detachFd() : -1;

Sorry,I've already checked the commit box :)
I've considered even writing a full if() statement to make it clearer (my
readability reviewer never believed in the ternary operator) but then decided
it'd be too much.

I don't have a strong opinion on this but my counterpoint would be that people
tend to better understand positive expressions rather than negative ones (e.g.
== vs != ) and it's also easier to visually parse fd.detachFd() out of the
statement since it's in the very end.

[commit-bot: I haz the power, 2014-09-03 17:38:37]

Committed patchset #1 (id:1) as d182e8ea88f3c24895cd183edea0154f7cc3707d

[commit-bot: I haz the power, 2014-09-10 03:26:38]

Patchset 1 (id:??) landed as
https://crrev.com/43fb252a05ebeb21097abb816d2ccea1ec84dbbc
Cr-Commit-Position: refs/heads/master@{#293164}