kernel/linux.git/mm/damon, branch v6.18.42

mm/damon/core: disallow overlapping input ranges for damon_set_regions()

2026-08-03T09:22:12+00:00

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/20260703165610.92894-1-sj@kernel.org Link: https://lore.kernel.org/20260630041806.151124-1-sj@kernel.org [1] Fixes: 97d482f4592f ("mm/damon/sysfs: reuse damon_set_regions() for regions setting") Signed-off-by: SJ Park Cc: # 5.19.x Signed-off-by: Andrew Morton Signed-off-by: SJ Park Signed-off-by: Greg Kroah-Hartman

mm/damon/core: validate ranges in damon_set_regions()

2026-08-03T09:22:12+00:00

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/20260630035221.146458-1-sj@kernel.org Fixes: 43b0536cb471 ("mm/damon: introduce DAMON-based Reclamation (DAMON_RECLAIM)") Signed-off-by: SJ Park Cc: Yang yingliang Cc: # 5.16.x Signed-off-by: Andrew Morton Signed-off-by: SJ Park Signed-off-by: Greg Kroah-Hartman

mm/damon/core: trace esz at first setup

2026-07-24T14:17:25+00:00

commit 7e6cc35f5283eab81a14231a64ecd640b690c48c upstream. DAMON traces effective size quota from the second update, only if a change has been made by the update. Tracing only changed updates was an intentional decision to avoid unnecessary same value tracing. Always skipping the first value is just an unintended mistake. The mistake makes the tracepoint based investigation incomplete, because the first effective size quota is never traced. It is not a big issue when the 'consist' quota tuner is used, because it keeps changing the quota in the usual setup. However, when the 'temporal' tuner is used, the quota value is not changed before the goal achievement status is completely changed. For example, if the DAMOS scheme is started with an under-achieved goal, the quota is set to the maximum value, and kept the same value until the goal is achieved. Because DAMON skips the first value, the user cannot know what effective quota the current scheme is using. Only after the goal is achieved, the effective quota is changed to zero, and traced. Unconditionally trace the initial quota value to fix this problem. Note that the 'temporal' quota tuner was introduced by commit af738a6a00c1 ("mm/damon/core: introduce DAMOS_QUOTA_GOAL_TUNER_TEMPORAL"), which was added to 7.1-rc1. But even with the 'consist' quota tuner, the tracing is unintentionally incomplete. Hence this commit marks the introduction of the trace event as the broken commit. Link: https://lore.kernel.org/20260520150311.80925-1-sj@kernel.org Fixes: a86d695193bf ("mm/damon: add trace event for effective size quota") Signed-off-by: SeongJae Park Cc: # 6.17.x Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

mm/damon/core: always put unsuccessfully committed target pids

2026-07-24T14:17:25+00:00

commit 6a66c557a2ab2609575bafd15e093669c05f9711 upstream. damon_commit_target() puts and gets the destination and the source target pids. It puts the destination target pid because it will be overwritten by the source target pid. It gets the source pid because the caller is supposed to eventually put the pids. In more detail, the caller will call damon_destroy_ctx() after damon_commit_ctx() to destroy the entire source context. And in this case, [f]vaddr operation set's cleanup_target() callback will put the pids. The commit operation is made at the context level. The operation can fail in multiple places including in the middle and after the targets commit operations. For any such failures, immediately the error is returned to the damon_commit_ctx() caller. If some or all of the source target pids were committed to the destination during the unsuccessful context commit attempt, those pids should be put twice. The source context will do the put operations using the above explained routine. However, let's suppose the destination context was not originally using [f]vaddr operation set and the commit failed before the ops of the source context is committed. The destination does not have the cleanup_target() ops callback, so it cannot put the pids via the damon_destroy_ctx(). As a result, the pids are leaked. The issue in the real world would be not very common. The commit feature is for changing parameters of running DAMON context while inheriting internal status like the monitoring results. The monitoring results of a physical address range ain't have things that are beneficial to be inherited to a virtual address ranges monitoring. So the problem-causing DAMON control would be not very common in the real world. That said, it is a supported feature. And damon_commit_target() failure due to memory allocation is relatively realistic [1] if there are a huge number of target regions. Fix by putting the pids in the commit operation in case of the failures. The issue was discovered [2] by Sashiko. Link: https://lore.kernel.org/20260605013849.83750-1-sj@kernel.org Link: https://lore.kernel.org/20260603112306.58490-1-akinobu.mita@gmail.com [1] Link: https://lore.kernel.org/20260320020056.835-1-sj@kernel.org [2] Fixes: 83dc7bbaecae ("mm/damon/sysfs: use damon_commit_ctx()") Signed-off-by: SeongJae Park Cc: # 6.11.x Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

mm/damon/sysfs-schemes: put stats for scheme_add_dirs() internal error

2026-07-24T14:17:01+00:00

commit 05ea83ee88ca70f8932906d9f2617ff996f45b50 upstream. damon_sysfs_scheme_add_dirs() setup the tried_regions directory after the stats directory setup is completed. When the tried_regions directory setup is failed, the setup function ensures the reference for the tried regions directory is released. Hence the error path should put references on setup succeeded directory objects, starting from the stats directory. However, the error path is putting the tried_regions directory instead of the stats directory. As a direct result, the stats directory object is leaked. Worse yet, if the tried_regions directory setup failed from the initial allocation, the scheme->tried_regions field remains uninitialized. The following kobject_put(&scheme->tried_regions->kobj) call in the error path will dereference the uninitialized memory. The setup failures should not be common. But once it happens, the consequence is quite bad. Fix this issue by correctly putting the stats directory instead of the tried_regions directory. The issue was discovered [1] by Sashiko. Link: https://lore.kernel.org/20260618005650.83868-3-sj@kernel.org Link: https://lore.kernel.org/20260617005223.96813-1-sj@kernel.org [1] Fixes: 5181b75f438d ("mm/damon/sysfs-schemes: implement schemes/tried_regions directory") Signed-off-by: SeongJae Park Cc: # 6.2.x Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

mm/damon/sysfs-schemes: fix dir put orders in access_pattern_add_dirs()

2026-07-24T14:17:01+00:00

commit d58fdbe37a829fd2e5803dd4e5a72992dd8c5368 upstream. Patch series "mm/damon/sysfs-schemes: fix wrong directories put orders in error paths". Error paths of damon_sysfs_access_pattern_add_dirs() and damon_sysfs_scheme_add_dirs() functions put references to directories in wrong orders. As a result, uninitialized memory dereference and/or memory leak can happen. Fix those. This patch (of 2): In access_pattern_add_dirs(), error handling path puts references starting from setup failed directories. If the failure happpened from the initial allication in the setup functions, uninitialized memory dereference happen. The allocation failures will not commonly happen, but the consequence is quite bad. Fix the wrong reference put orders. The issue was discovered [1] by Sashiko. Link: https://lore.kernel.org/20260618005650.83868-2-sj@kernel.org Link: https://lore.kernel.org/20260617060005.86852-1-sj@kernel.org [1] Fixes: 7e84b1f8212a ("mm/damon/sysfs: support DAMON-based Operation Schemes") Signed-off-by: SeongJae Park Cc: # 5.18.x Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

mm/damon/core: make charge_addr_from aware of end-address exclusivity

2026-07-24T14:17:00+00:00

commit 5a2d162e22bf33eb89d53e802d0fc1ec422e19b6 upstream. DAMON region end address is exclusive one, but charge_addr_from is assigned assuming the end address is inclusive. As a result, DAMOS action to next up to min_region_sz memory can be skipped. This is quite negligible user impact. But, the bug is a bug that can be very simply fixed. Fix the wrong assignment to respect the exclusiveness of the address. The issue was discovered [1] by Sashiko. Link: https://lore.kernel.org/20260428042942.118230-1-sj@kernel.org Link: https://lore.kernel.org/20260428032324.115663-1-sj@kernel.org [1] Fixes: 50585192bc2e ("mm/damon/schemes: skip already charged targets and regions") Signed-off-by: SeongJae Park Cc: # 5.16.x Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

mm/damon/ops-common: handle extreme intervals in damon_hot_score()

2026-07-18T14:53:13+00:00

commit 35d4a3cf70a855b50e53189ac2f8463e20a02046 upstream. Fix three issues in damon_hot_score() that comes from wrong handling of extreme (zero or too high) monitoring intervals user setup. When the user sets sampling interval zero, damon_max_nr_accesses(), which is called from damon_hot_score(), causes a divide-by-zero. Needless to say, it is a problem. When the user sets the aggregation interval zero, the function returns zero. It is wrong, since the real maximum nr_acceses in the setup should be one. Worse yet, it can cause another divide-by-zero from its caller, damon_hot_score(), since it uses damon_max_nr_accesses() return value as a denominator. When the user sets the aggregation interval very high, damon_hot_score() could return a value out of [0, DAMOS_MAX_SCORE] range. Since the return value is used as an index to the regions_score_histogram array, which is DAMOS_MAX_SCORE+1 size, it causes out of bounds array access. The issues can be relatively easily reproduced like below. The sysfs write permission is required, though. # ./damo start --damos_action lru_prio --damos_quota_space 100M \ --damos_quota_interval 1s # cd /sys/kernel/mm/damon/admin/kdamonds/0 # echo 0 > contexts/0/monitoring_attrs/intervals/sample_us # echo 0 > contexts/0/monitoring_attrs/intervals/aggr_us # echo commit > state # dmesg [...] [ 131.329762] Oops: divide error: 0000 [#1] SMP NOPTI [...] [ 131.336089] RIP: 0010:damon_hot_score+0x27/0xd0 [...] Fix the divide-by-zero intervals problems by explicitly handling the zero intervals in damon_max_nr_accesses(). Fix the out-of-bound array access by applying [0, DAMOS_MAX_SCORE] bounds before returning from damon_hot_score(). The issue was discovered [1] by Sashiko. Link: https://lore.kernel.org/20260623135834.67189-1-sj@kernel.org Link: https://lore.kernel.org/20260619202459.145010-1-sj@kernel.org [1] Fixes: 198f0f4c58b9 ("mm/damon/vaddr,paddr: support pageout prioritization") Signed-off-by: SeongJae Park Cc: # 5.16.x Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

mm/damon/reclaim: handle ctx allocation failure

2026-06-19T11:44:10+00:00

commit 7e2ed8a29427af534bf2cb9b8bc51762b8b6e654 upstream. Patch series "mm/damon/{reclaim,lru_sort}: handle ctx allocation failures". DAMON_RECLAIM and DAMON_LRU_SORT could dereference NULL pointers if their damon_ctx object allocations fail. The bugs are expected to happen infrequently because the allocations are arguably too small to fail on common setups. But theoretically they are possible and the consequences are bad. Fix those. The issues were discovered [1] by Sashiko. This patch (of 2): DAMON_RECLAIM allocates the damon_ctx object for its kdamond in its init function. damon_reclaim_enabled_store() wrongly assumes the allocation will always succeed once tried. If the damon_ctx allocation was failed, therefore, code execution reaches to damon_commit_ctx() while 'ctx' is NULL. As a result, it dereferences the NULL 'ctx' pointer. Avoid the NULL dereference by returning -ENOMEM if 'ctx' is NULL. Link: https://lore.kernel.org/20260529000104.7006-2-sj@kernel.org Link: https://lore.kernel.org/20260419014800.877-1-sj@kernel.org [1] Fixes: 3f7a914ab9a5 ("mm/damon/reclaim: use damon_initialized()") Signed-off-by: SeongJae Park Cc: # 6.18.x Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

mm/damon/lru_sort: handle ctx allocation failure

2026-06-19T11:44:10+00:00

commit ab04340b5ae5d52c1d46b750538febcde9d889e7 upstream. DAMON_LRU_SORT allocates the damon_ctx object for its kdamond in its init function. damon_lru_sort_enabled_store() wrongly assumes the allocation will always succeed once tried. If the damon_ctx allocation was failed, therefore, code execution reaches to damon_commit_ctx() while 'ctx' is NULL. As a result, it dereferences the NULL 'ctx' pointer. Avoid the NULL dereference by returning -ENOMEM if 'ctx' is NULL. Link: https://lore.kernel.org/20260529000104.7006-3-sj@kernel.org Fixes: c4a8e662c839 ("mm/damon/lru_sort: use damon_initialized()") Signed-off-by: SeongJae Park Cc: # 6.18.x Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman