From manual code review, I found below bugs in DAMON modules.
DAMON sample modules crash if those are enabled at boot time, via kernel command line. A similar issue was found and fixed on DAMON non-sample modules in the past, but we didn't check that for sample modules.
DAMON non-sample modules are not setting 'enabled' parameters accordingly when real enabling is failed. Honggyu found and fixed[1] this type of bugs in DAMON sample modules, and my inspection was motivated by the great work. Kudos to Honggyu.
Finally, DAMON_RECLIAM is mistakenly losing scheme internal status due to misuse of damon_commit_ctx(). DAMON_LRU_SORT has a similar misuse, but fortunately it is not causing real status loss.
Fix the bugs. Since these are similar patterns of bugs that were found in the past, it would be better to add tests or refactor the code, in future.
Note that the fix of the second bug for DAMON_STAT is sent separately[2], since it is a fix for a bug in mm-unstable tree at the moment. Also as mentioned above, DAMON_LRU_SORT also has a misuse of damon_commit_ctx(), but it is not causing a real issue, hence the fix is not included in this series. I will post it later.
[1] https://lore.kernel.org/20250702000205.1921-1-honggyu.kim@sk.com [2] https://lore.kernel.org/20250706184750.36588-1-sj@kernel.org
SeongJae Park (6): samples/damon/wsse: fix boot time enable handling samples/damon/prcl: fix boot time enable crash samples/damon/mtier: support boot time enable setup mm/damon/reclaim: reset enabled when DAMON start failed mm/damon/lru_sort: reset enabled when DAMON start failed mm/damon/reclaim: use parameter context correctly
mm/damon/lru_sort.c | 5 ++++- mm/damon/reclaim.c | 9 ++++++--- samples/damon/mtier.c | 13 +++++++++++++ samples/damon/prcl.c | 13 +++++++++++++ samples/damon/wsse.c | 15 ++++++++++++++- 5 files changed, 50 insertions(+), 5 deletions(-)
base-commit: a555ad24c884e9f4ee2f2a0184f5b7b89c8d4a6e
If 'enable' parameter of the 'wsse' DAMON sample module is set at boot time via the kernel command line, memory allocation is tried before the slab is initialized. As a result kernel NULL pointer dereference BUG can happen. Fix it by checking the initialization status.
Fixes: b757c6cfc696 ("samples/damon/wsse: start and stop DAMON as the user requests") Cc: stable@vger.kernel.org Signed-off-by: SeongJae Park sj@kernel.org --- samples/damon/wsse.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-)
diff --git a/samples/damon/wsse.c b/samples/damon/wsse.c index e20238a249e7..15e2683fe5f3 100644 --- a/samples/damon/wsse.c +++ b/samples/damon/wsse.c @@ -89,6 +89,8 @@ static void damon_sample_wsse_stop(void) put_pid(target_pidp); }
+static bool init_called; + static int damon_sample_wsse_enable_store( const char *val, const struct kernel_param *kp) { @@ -103,6 +105,9 @@ static int damon_sample_wsse_enable_store( return 0;
if (enable) { + if (!init_called) + return 0; + err = damon_sample_wsse_start(); if (err) enable = false; @@ -114,7 +119,15 @@ static int damon_sample_wsse_enable_store(
static int __init damon_sample_wsse_init(void) { - return 0; + int err = 0; + + init_called = true; + if (enable) { + err = damon_sample_wsse_start(); + if (err) + enable = false; + } + return err; }
module_init(damon_sample_wsse_init);
If 'enable' parameter of the 'mtier' DAMON sample module is set at boot time via the kernel command line, memory allocation is tried before the slab is initialized. As a result kernel NULL pointer dereference BUG can happen. Fix it by checking the initialization status.
Fixes: 82a08bde3cf7 ("samples/damon: implement a DAMON module for memory tiering") Cc: stable@vger.kernel.org Signed-off-by: SeongJae Park sj@kernel.org --- samples/damon/mtier.c | 13 +++++++++++++ 1 file changed, 13 insertions(+)
diff --git a/samples/damon/mtier.c b/samples/damon/mtier.c index 97892ade7f31..20c3102242ec 100644 --- a/samples/damon/mtier.c +++ b/samples/damon/mtier.c @@ -157,6 +157,8 @@ static void damon_sample_mtier_stop(void) damon_destroy_ctx(ctxs[1]); }
+static bool init_called; + static int damon_sample_mtier_enable_store( const char *val, const struct kernel_param *kp) { @@ -170,6 +172,9 @@ static int damon_sample_mtier_enable_store( if (enable == enabled) return 0;
+ if (!init_called) + return 0; + if (enable) { err = damon_sample_mtier_start(); if (err) @@ -182,6 +187,14 @@ static int damon_sample_mtier_enable_store(
static int __init damon_sample_mtier_init(void) { + int err = 0; + + init_called = true; + if (enable) { + err = damon_sample_mtier_start(); + if (err) + enable = false; + } return 0; }
linux-stable-mirror@lists.linaro.org
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SeongJae Park