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| author | Josh Law <objecting@objecting.org> | 2026-03-21 10:54:26 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2026-04-02 13:23:25 +0200 |
| commit | 3527e9fdc38570cea0f6ddb7a2c9303d4044b217 (patch) | |
| tree | bb27df06cc72cb7054494b9fc437ce6f1a6629d8 /mm | |
| parent | 708033c231bd782858f4ddbb46ee874a5a5fbdab (diff) | |
| download | linux-3527e9fdc38570cea0f6ddb7a2c9303d4044b217.tar.gz linux-3527e9fdc38570cea0f6ddb7a2c9303d4044b217.tar.bz2 linux-3527e9fdc38570cea0f6ddb7a2c9303d4044b217.zip | |
mm/damon/sysfs: check contexts->nr in repeat_call_fn
commit 6557004a8b59c7701e695f02be03c7e20ed1cc15 upstream.
damon_sysfs_repeat_call_fn() calls damon_sysfs_upd_tuned_intervals(),
damon_sysfs_upd_schemes_stats(), and
damon_sysfs_upd_schemes_effective_quotas() without checking contexts->nr.
If nr_contexts is set to 0 via sysfs while DAMON is running, these
functions dereference contexts_arr[0] and cause a NULL pointer
dereference. Add the missing check.
For example, the issue can be reproduced using DAMON sysfs interface and
DAMON user-space tool (damo) [1] like below.
$ sudo damo start --refresh_interval 1s
$ echo 0 | sudo tee \
/sys/kernel/mm/damon/admin/kdamonds/0/contexts/nr_contexts
Link: https://patch.msgid.link/20260320163559.178101-3-objecting@objecting.org
Link: https://lkml.kernel.org/r/20260321175427.86000-4-sj@kernel.org
Link: https://github.com/damonitor/damo [1]
Fixes: d809a7c64ba8 ("mm/damon/sysfs: implement refresh_ms file internal work")
Signed-off-by: Josh Law <objecting@objecting.org>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: <stable@vger.kernel.org> [6.17+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/damon/sysfs.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/mm/damon/sysfs.c b/mm/damon/sysfs.c index 28794e191c19..61c7b799bf83 100644 --- a/mm/damon/sysfs.c +++ b/mm/damon/sysfs.c @@ -1570,9 +1570,12 @@ static int damon_sysfs_repeat_call_fn(void *data) if (!mutex_trylock(&damon_sysfs_lock)) return 0; + if (sysfs_kdamond->contexts->nr != 1) + goto out; damon_sysfs_upd_tuned_intervals(sysfs_kdamond); damon_sysfs_upd_schemes_stats(sysfs_kdamond); damon_sysfs_upd_schemes_effective_quotas(sysfs_kdamond); +out: mutex_unlock(&damon_sysfs_lock); return 0; } |