diff options
| author | Stanislav Fort <stanislav.fort@aisle.com> | 2025-09-05 13:10:46 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-09-19 16:35:47 +0200 |
| commit | 26d29b2ac87a2989071755f9828ebf839b560d4c (patch) | |
| tree | 719c5cef3feca17542ba9b33dd73d8a0429f08b7 | |
| parent | 305935130d5493d447961e3e449a5f7438c01260 (diff) | |
mm/damon/sysfs: fix use-after-free in state_show()
commit 3260a3f0828e06f5f13fac69fb1999a6d60d9cff upstream.
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.
Link: https://lkml.kernel.org/r/20250905101046.2288-1-disclosure@aisle.com
Fixes: a61ea561c871 ("mm/damon/sysfs: link DAMON for virtual address spaces monitoring")
Signed-off-by: Stanislav Fort <disclosure@aisle.com>
Reported-by: Stanislav Fort <disclosure@aisle.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | mm/damon/sysfs.c | 14 |
1 files changed, 9 insertions, 5 deletions
diff --git a/mm/damon/sysfs.c b/mm/damon/sysfs.c index 58145d59881d..9ce2abc64de4 100644 --- a/mm/damon/sysfs.c +++ b/mm/damon/sysfs.c @@ -1067,14 +1067,18 @@ static ssize_t state_show(struct kobject *kobj, struct kobj_attribute *attr, { struct damon_sysfs_kdamond *kdamond = container_of(kobj, struct damon_sysfs_kdamond, kobj); - struct damon_ctx *ctx = kdamond->damon_ctx; - bool running; + struct damon_ctx *ctx; + bool running = false; - if (!ctx) - running = false; - else + if (!mutex_trylock(&damon_sysfs_lock)) + return -EBUSY; + + ctx = kdamond->damon_ctx; + if (ctx) running = damon_sysfs_ctx_running(ctx); + mutex_unlock(&damon_sysfs_lock); + return sysfs_emit(buf, "%s\n", running ? damon_sysfs_cmd_strs[DAMON_SYSFS_CMD_ON] : damon_sysfs_cmd_strs[DAMON_SYSFS_CMD_OFF]); |