Linux-stable-mirror January 2026

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2 discussions

[PATCH] mm/damon/core: remove call_control in inactive contexts

by SeongJae Park

If damon_call() is executed against a DAMON context that is not running, the function returns error while keeping the damon_call_control object linked to the context's call_controls list. Let's suppose the object is deallocated after the damon_call(), and yet another damon_call() is executed against the same context. The function tries to add the new damon_call_control object to the call_controls list, which still has the pointer to the previous damon_call_control object, which is deallocated. As a result, use-after-free happens. This can actually be triggered using the DAMON sysfs interface. It is not easily exploitable since it requires the sysfs write permission and making a definitely weird file writes, though. Please refer to the report for more details about the issue reproduction steps. Fix the issue by making damon_call() to cleanup the damon_call_control object before returning the error. Reported-by: JaeJoon Jung <rgbi3307(a)gmail.com> Closes: https://lore.kernel.org/20251224094401.20384-1-rgbi3307@gmail.com Fixes: 42b7491af14c ("mm/damon/core: introduce damon_call()") Cc: <stable(a)vger.kernel.org> # 6.14.x Signed-off-by: SeongJae Park <sj(a)kernel.org> --- mm/damon/core.c | 31 ++++++++++++++++++++++++++++++- 1 file changed, 30 insertions(+), 1 deletion(-) diff --git a/mm/damon/core.c b/mm/damon/core.c index 2d3e8006db50..65482a0ce20b 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -1442,6 +1442,35 @@ bool damon_is_running(struct damon_ctx *ctx) return running; } +/* + * damon_call_handle_inactive_ctx() - handle DAMON call request that added to + * an inactive context. + * @ctx: The inactive DAMON context. + * @control: Control variable of the call request. + * + * This function is called in a case that @control is added to @ctx but @ctx is + * not running (inactive). See if @ctx handled @control or not, and cleanup + * @control if it was not handled. + * + * Returns 0 if @control was handled by @ctx, negative error code otherwise. + */ +static int damon_call_handle_inactive_ctx( + struct damon_ctx *ctx, struct damon_call_control *control) +{ + struct damon_call_control *c; + + mutex_lock(&ctx->call_controls_lock); + list_for_each_entry(c, &ctx->call_controls, list) { + if (c == control) { + list_del(&control->list); + mutex_unlock(&ctx->call_controls_lock); + return -EINVAL; + } + } + mutex_unlock(&ctx->call_controls_lock); + return 0; +} + /** * damon_call() - Invoke a given function on DAMON worker thread (kdamond). * @ctx: DAMON context to call the function for. @@ -1472,7 +1501,7 @@ int damon_call(struct damon_ctx *ctx, struct damon_call_control *control) list_add_tail(&control->list, &ctx->call_controls); mutex_unlock(&ctx->call_controls_lock); if (!damon_is_running(ctx)) - return -EINVAL; + return damon_call_handle_inactive_ctx(ctx, control); if (control->repeat) return 0; wait_for_completion(&control->completion); base-commit: a100272b3541cb00a5e29fdc16e428234ebfddd1 -- 2.47.3

18 minutes

[PATCH] mm/zswap: fix error pointer free in zswap_cpu_comp_prepare()

by Pavel Butsykin

crypto_alloc_acomp_node() may return ERR_PTR(), but the fail path checks only for NULL and can pass an error pointer to crypto_free_acomp(). Use IS_ERR_OR_NULL() to only free valid acomp instances. Fixes: 779b9955f643 ("mm: zswap: move allocations during CPU init outside the lock") Cc: stable(a)vger.kernel.org Signed-off-by: Pavel Butsykin <pbutsykin(a)cloudlinux.com> --- mm/zswap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/zswap.c b/mm/zswap.c index 5d0f8b13a958..ac9b7a60736b 100644 --- a/mm/zswap.c +++ b/mm/zswap.c @@ -787,7 +787,7 @@ static int zswap_cpu_comp_prepare(unsigned int cpu, struct hlist_node *node) return 0; fail: - if (acomp) + if (!IS_ERR_OR_NULL(acomp)) crypto_free_acomp(acomp); kfree(buffer); return ret; -- 2.52.0

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Linux-stable-mirror January 2026