Public bug reported:
I got a building failure with resolute derivative kernel, in this
kernel, the CONFIG_DAMON is enabled, then I got the building error:
CC lib/string.o
In file included from /<<PKGBUILDDIR>>/include/vdso/const.h:5,
from /<<PKGBUILDDIR>>/include/linux/const.h:4,
from /<<PKGBUILDDIR>>/include/uapi/linux/kernel.h:6,
from /<<PKGBUILDDIR>>/include/linux/cache.h:5,
from /<<PKGBUILDDIR>>/arch/arm64/include/asm/processor.h:31,
from /<<PKGBUILDDIR>>/include/linux/sched.h:13,
from /<<PKGBUILDDIR>>/include/linux/cgroup.h:12,
from /<<PKGBUILDDIR>>/include/linux/memcontrol.h:13,
from /<<PKGBUILDDIR>>/include/linux/damon.h:11,
from /<<PKGBUILDDIR>>/mm/damon/core.c:10:
/<<PKGBUILDDIR>>/mm/damon/core.c: In function ‘damon_set_regions’:
/<<PKGBUILDDIR>>/mm/damon/core.c:224:53: error: ‘min_sz_region’ undeclared
(first use in this function); did you mean ‘damon_sz_region’?
224 | start = ALIGN_DOWN(ranges[i].start, min_sz_region);
| ^~~~~~~~~~~~~
/<<PKGBUILDDIR>>/include/uapi/linux/const.h:49:44: note: in definition of macro
‘__ALIGN_KERNEL_MASK’
49 | #define __ALIGN_KERNEL_MASK(x, mask) (((x) + (mask)) & ~(mask))
| ^
/<<PKGBUILDDIR>>/include/vdso/align.h:9:33: note: in expansion of macro
‘__ALIGN_KERNEL’
9 | #define ALIGN_DOWN(x, a) __ALIGN_KERNEL((x) - ((a) - 1), (a))
| ^~~~~~~~~~~~~~
/<<PKGBUILDDIR>>/mm/damon/core.c:224:25: note: in expansion of macro
‘ALIGN_DOWN’
224 | start = ALIGN_DOWN(ranges[i].start, min_sz_region);
| ^~~~~~~~~~
/<<PKGBUILDDIR>>/mm/damon/core.c:224:53: note: each undeclared identifier is
reported only once for each function it appears in
224 | start = ALIGN_DOWN(ranges[i].start, min_sz_region);
| ^~~~~~~~~~~~~
/<<PKGBUILDDIR>>/include/uapi/linux/const.h:49:44: note: in definition of macro
‘__ALIGN_KERNEL_MASK’
49 | #define __ALIGN_KERNEL_MASK(x, mask) (((x) + (mask)) & ~(mask))
| ^
/<<PKGBUILDDIR>>/include/vdso/align.h:9:33: note: in expansion of macro
‘__ALIGN_KERNEL’
9 | #define ALIGN_DOWN(x, a) __ALIGN_KERNEL((x) - ((a) - 1), (a))
| ^~~~~~~~~~~~~~
/<<PKGBUILDDIR>>/mm/damon/core.c:224:25: note: in expansion of macro
‘ALIGN_DOWN’
224 | start = ALIGN_DOWN(ranges[i].start, min_sz_region);
| ^~~~~~~~~~
make[6]: *** [/<<PKGBUILDDIR>>/scripts/Makefile.build:289: mm/damon/core.o]
Error 1
make[5]: *** [/<<PKGBUILDDIR>>/scripts/Makefile.build:548: mm/damon] Error 2
make[4]: *** [/<<PKGBUILDDIR>>/scripts/Makefile.build:548: mm] Error 2
make[4]: *** Waiting for unfinished jobs....
The culprit commits are introduced in the resolute:7.0.0-38.38, and they are:
commit ca3fcff334db5a711a67e719c9f04ea23312cce8
Author: SJ Park <[email protected]>
Date: Fri Jul 3 09:56:08 2026 -0700
mm/damon/core: disallow overlapping input ranges for damon_set_regions()
BugLink: https://bugs.launchpad.net/bugs/2165189
commit 954157679ec34661c2e87e7eb796104a797c32db upstream.
damon_set_regions() assumes the input ranges are sorted by the address and
don't overlap each other. Hence the assumption was initially to be
explicitly validated. But commit 97d482f4592f ("mm/damon/sysfs: reuse
damon_set_regions() for regions setting") has mistakenly removed the
validation.
This can make DAMON behave in unexpected ways. At the best, the
monitoring results snapshot will just look weird since there will be
overlapping regions. DAMOS will also work weirdly, applying the same
action multiple times for overlapping regions, and make DAMOS quota weird.
More seriously, depending on the setup and regions updates sequence,
negative size regions can be made. It will trigger WARN_ONCE() if the
kernel is built with CONFIG_DAMON_DEBUG_SANITY=y. Depending on the
monitoring results, the negative size region can further trigger division
by zero in damon_merge_two_regions().
Note that some of the consequences including the WARN_ONCE() and the
divide by zero depend on commits that were introduced after the root cause
commit 97d482f4592f ("mm/damon/sysfs: reuse damon_set_regions() for
regions setting").
Fix the problems by checking the assumption and returning an error if
the input ranges don't meet the assumption.
The issue was discovered [1] by Sashiko.
Link: https://lore.kernel.org/[email protected]
Link: https://lore.kernel.org/[email protected] [1]
Fixes: 97d482f4592f ("mm/damon/sysfs: reuse damon_set_regions() for regions
setting")
Signed-off-by: SJ Park <[email protected]>
Cc: <[email protected]> # 5.19.x
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: SJ Park <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
CVE-2026-68164
Signed-off-by: Alice C. Munduruca <[email protected]>
Signed-off-by: Edoardo Canepa <[email protected]>
commit 1f2b831fd3135866dd0f6d5d3f74e0e8466a42d8
Author: SJ Park <[email protected]>
Date: Mon Jun 29 20:52:19 2026 -0700
mm/damon/core: validate ranges in damon_set_regions()
BugLink: https://bugs.launchpad.net/bugs/2165189
commit 1292c0ecb1caefb8ca064a3639d5673991e8810c upstream.
DAMON core logic assumes zero length regions don't exist. However, a few
DAMON API callers including DAMON_SYSFS, DAMON_RECLAIM and DAMON_LRU_SORT
allow users to set empty monitoring target regions. This could result in
WARN_ONCE() on CONFIG_DAMON_DEBUG_SANITY enabled kernel, and
divide-by-zero from damon_merge_two_regions().
For example, the WANR_ONCE() can be triggered like below.
# grep DAMON_DEBUG_SANITY /boot/config-$(uname -r)
# CONFIG_DAMON_DEBUG_SANITY=y
# damo start
# cd /sys/kernel/mm/damon/admin/kdamonds/0
# echo 0 > contexts/0/targets/0/regions/0/start
# echo 0 > contexts/0/targets/0/regions/0/end
# echo commit > state
# dmesg
[....]
[ 73.705780] ------------[ cut here ]------------
[ 73.707552] start 0 >= end 0
[ 73.708452] WARNING: mm/damon/core.c:359 at
damon_new_region+0x6e/0x80, CPU#1: kdamond.0/758
[...]
All DAMON API callers eventually use damon_set_regions() to setup the
regions. Add the validation logic in the function.
Link: https://lore.kernel.org/[email protected]
Fixes: 43b0536cb471 ("mm/damon: introduce DAMON-based Reclamation
(DAMON_RECLAIM)")
Signed-off-by: SJ Park <[email protected]>
Cc: Yang yingliang <[email protected]>
Cc: <[email protected]> # 5.16.x
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: SJ Park <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
CVE-2026-68165
Signed-off-by: Alice C. Munduruca <[email protected]>
Signed-off-by: Edoardo Canepa <[email protected]>
Looks like the min_sz_region should be replaced with min_region_sz.
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
** Affects: linux (Ubuntu Resolute)
Importance: Undecided
Status: New
** Also affects: linux (Ubuntu Resolute)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/2168390
Title:
Build failure on /mm/damon/core.c when CONFIG_DAMON is enabled
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