Messages in this thread |  | | From | SeongJae Park <> | | Subject | Re: [PATCH v2] mm/damon/sysfs: fix use-after-free in state_show() | | Date | Fri, 5 Sep 2025 13:12:50 -0700 |
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+ Andrew
On Fri, 5 Sep 2025 13:10:46 +0300 Stanislav Fort <stanislav.fort@aisle.com> wrote:
> state_show() reads kdamond->damon_ctx without holding damon_sysfs_lock. > This allows a use-after-free race: > > CPU 0 CPU 1 > ----- ----- > state_show() damon_sysfs_turn_damon_on() > ctx = kdamond->damon_ctx; mutex_lock(&damon_sysfs_lock); > damon_destroy_ctx(kdamond->damon_ctx); > kdamond->damon_ctx = NULL; > mutex_unlock(&damon_sysfs_lock); > damon_is_running(ctx); /* ctx is freed */ > mutex_lock(&ctx->kdamond_lock); /* UAF */ > > (The race can also occur with damon_sysfs_kdamonds_rm_dirs() and > damon_sysfs_kdamond_release(), which free or replace the context under > damon_sysfs_lock.) > > Fix by taking damon_sysfs_lock before dereferencing the context, > mirroring the locking used in pid_show(). > > The bug has existed since state_show() first accessed kdamond->damon_ctx. > > Fixes: a61ea561c871 ("mm/damon/sysfs: link DAMON for virtual address spaces monitoring") > Reported-by: Stanislav Fort <disclosure@aisle.com> > Closes: N/A # non-publicly reported > Signed-off-by: Stanislav Fort <disclosure@aisle.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Thanks, SJ
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