Hello Greg, Hello Filipe,
On Sun, Aug 13, 2023 at 12:34:08PM +0100, fdmanana@kernel.org wrote:
From: Filipe Manana fdmanana@suse.com
The readdir implementation currently processes always up to the last index it finds. This however can result in an infinite loop if the directory has a large number of entries such that they won't all fit in the given buffer passed to the readdir callback, that is, dir_emit() returns a non-zero value. Because in that case readdir() will be called again and if in the meanwhile new directory entries were added and we still can't put all the remaining entries in the buffer, we keep repeating this over and over.
The following C program and test script reproduce the problem:
This crucial fix successfully landed into vanilla v6.5 [1] and stable v6.4.12 [2], but unfortunately not into the older stable trees.
Consequently, the fix is missing on the popular Ubuntu versions like 20.04 (KNL v5.15.x) and 22.04.3 (KNL v6.2.x). For that reason, people still experience infinite loops when building Linux on those systems.
To overcome the issue, people fall back to workarounds [3-4].
The patch seems to apply cleanly to v6.2, but not to v5.15 (v5.15 backport attempt failed miserably).
Is there a chance for: - Stable maintainers to accept the clean backport to v6.2? - BTRFS experts to suggest a conflict resolution for v5.15?
[1] https:// git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=9b378f6ad48cfa [2] https:// git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5441532ffc9c8c [3] https:// android-review.googlesource.com/c/kernel/build/+/2708835 [4] https:// android-review.googlesource.com/c/kernel/build/+/2715296
Best Regards Eugeniu