_kern_read_link changes cause ls to crash

[waddlesplash]

1. Run ls -alR /system/add-ons
2. Crash!

This is with coreutils-8.29-2 (i.e. the version that we have been bundling with Haiku since over a month ago.)

I'm not sure if this was always present on this version, or nobody noticed until now. Either way, seems serious enough to be a blocker.

[waddlesplash]

(I had a libroot in non-packaged with rpmalloc; the equivalent assert in hoard2 occurs also.)

Multiple users on IRC reported this, and it reproduces in a fresh build of both x86_64 and x86_gcc2h.

[waddlesplash]

For some reason, it does not reproduce with the guarded heap. With the debug heap:

        state: Call (someone wrote beyond small allocation at 0x180062d0; size: 0 bytes; allocated by 0; value: 0x0000002e

[waddlesplash]

areadlink_with_size: ​https://github.com/coreutils/gnulib/blob/master/lib/areadlink-with-size.c#L51

[waddlesplash]

CC ambroff: your readlink change looks notable. Checking to see if that is the culprit now...

[waddlesplash]

Reverting hrev54107 fixed the crash. ambroff, can you please take a look? At worst we could revert this in the beta branch, but a proper fix would indeed be nice.

[ambroff]

Dang, thanks for reverting waddlesplash. I'll look into it today or tomorrow if time permits.

[korli]

I took a deeper look:

Not related, shouldn't rootfs and devfs readlink behavior also changed? ​https://github.com/haiku/haiku/blob/master/src/system/kernel/fs/rootfs.cpp#L862 ​https://github.com/haiku/haiku/blob/master/src/system/kernel/device_manager/devfs.cpp#L1180

The checksumfs looks also to be changed: ​https://github.com/haiku/haiku/blob/master/src/tests/system/kernel/file_corruption/fs/SymLink.cpp#L62

The write_overlay looks also to be changed: ​https://github.com/haiku/haiku/blob/master/src/add-ons/kernel/file_systems/layers/write_overlay/write_overlay.cpp#L1062

Also vfs null-terminates on success, this looks not OK (size should be checked against B_PATH_NAME_LENGTH at least) ​https://github.com/haiku/haiku/blob/master/src/system/kernel/fs/vfs.cpp#L2252 ​https://github.com/haiku/haiku/blob/master/src/system/kernel/fs/vfs.cpp#L2956

_user_read_link behavior is now bad, it will write after the buffer end, anytime the buffer is too short. It should honor the user bufferSize, instead of using the link length. ​https://github.com/haiku/haiku/blob/master/src/system/kernel/fs/vfs.cpp#L9418

[waddlesplash]

korli's changes merged in hrev54234. I did not retest if this fixes the problem though.

[korli]

yes it fixes the problem in master. I added ​https://review.haiku-os.org/c/haiku/+/2761 to expose the symlink string length in package nodes (this would have been a workaround for the bug).

[ambroff]

Thank you korli for looking at this and fixing all of these issues that I left dangling. Sorry that I took so long. I've been busy the last couple of days.