The patch titled
Subject: mm/hmm: prevent infinite loop in hmm_range_fault during EBUSY retries
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-hmm-prevent-infinite-loop-in-hmm_range_fault-during-ebusy-retries.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-hmm-prevent-infinite-loop-in-hmm_range_fault-during-ebusy-retries.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: sooraj <sooraj20636@xxxxxxxxx>
Subject: mm/hmm: prevent infinite loop in hmm_range_fault during EBUSY retries
Date: Tue, 28 Jan 2025 01:34:22 -0500
When hmm_vma_walk_test() skips a VMA (e.g., unsupported VM_IO/PFNMAP
range), it must update hmm_vma_walk->last to the end of the skipped VMA.
Failing to do so causes hmm_range_fault() to restart from the same address
during -EBUSY retries, reprocessing the skipped VMA indefinitely. This
results in an infinite loop if the VMA remains non-processable.
Update hmm_vma_walk->last to the VMA's end address in hmm_vma_walk_test()
when skipping the range. This ensures subsequent iterations resume
correctly after the skipped VMA, preventing infinite retry loops.
Link: https://lkml.kernel.org/r/20250128063422.7604-1-sooraj20636@xxxxxxxxx
Signed-off-by: sooraj <sooraj20636@xxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxxxx>
Cc: Jerome Glisse <jglisse@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/hmm.c | 2 ++
1 file changed, 2 insertions(+)
--- a/mm/hmm.c~mm-hmm-prevent-infinite-loop-in-hmm_range_fault-during-ebusy-retries
+++ a/mm/hmm.c
@@ -547,6 +547,8 @@ static int hmm_vma_walk_test(unsigned lo
hmm_pfns_fill(start, end, range, HMM_PFN_ERROR);
+ /* Update last to the end of the skipped VMA to prevent reprocessing */
+ hmm_vma_walk->last = end;
/* Skip this vma and continue processing the next vma. */
return 1;
}
_
Patches currently in -mm which might be from sooraj20636@xxxxxxxxx are
mm-hmm-prevent-infinite-loop-in-hmm_range_fault-during-ebusy-retries.patch
