On 2019/08/02 3:50, Luis Chamberlain wrote:
> That's quite an opaque commit log for what started off as a severe email
> thread of potential leak of information. As such, can you expand on this
> commit log considerably to explain the situation a bit better? Your
> initial thread here provided much clearer evidence of the issue. As-is
> this commit log tells the reader *nothing* about the potential harm in
> not applying this patch.
>
> You had mentioned you identified this issue present on at least
> 4.18 till 5.3-rc1. So, I'm at least inclined to consider this for
> stable for at least v4.19.
>
> However, what about older kernels? Now that you have identified
> a fix, were the flag changed in prior commits, is it a regression
> that perhaps added KM_MAYFAIL at some point?
I only checked 4.18+ so that RHEL8 will backport this patch. According to
Brian Foster, commit eb01c9cd87 ("[XFS] Remove the xlog_ticket allocator")
( https://git.kernel.org/linus/eb01c9cd87 ) which dates back to April 2008
added KM_MAYFAIL flag for this allocation
- buf = (xfs_caddr_t) kmem_zalloc(PAGE_SIZE, KM_SLEEP);
+ tic = kmem_zone_zalloc(xfs_log_ticket_zone, KM_SLEEP|KM_MAYFAIL);
though Dave Chinner thinks that the log ticket rework is irrelevant.
Do we need to find which commit made this problem visible?
