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authorJohannes Weiner <hannes@cmpxchg.org>2023-10-26 12:41:14 -0400
committerPeter Zijlstra <peterz@infradead.org>2023-11-14 22:27:00 +0100
commit8b39d20eceeda6c4eb23df1497f9ed2fffdc8f69 (patch)
tree2e6ff440b1eee46ae239295fb5bf90a15547b0d1
parenteab03c23c2a162085b13200d7942fc5a00b5ccc8 (diff)
sched: psi: fix unprivileged polling against cgroups
519fabc7aaba ("psi: remove 500ms min window size limitation for triggers") breaks unprivileged psi polling on cgroups. Historically, we had a privilege check for polling in the open() of a pressure file in /proc, but were erroneously missing it for the open() of cgroup pressure files. When unprivileged polling was introduced in d82caa273565 ("sched/psi: Allow unprivileged polling of N*2s period"), it needed to filter privileges depending on the exact polling parameters, and as such moved the CAP_SYS_RESOURCE check from the proc open() callback to psi_trigger_create(). Both the proc files as well as cgroup files go through this during write(). This implicitly added the missing check for privileges required for HT polling for cgroups. When 519fabc7aaba ("psi: remove 500ms min window size limitation for triggers") followed right after to remove further restrictions on the RT polling window, it incorrectly assumed the cgroup privilege check was still missing and added it to the cgroup open(), mirroring what we used to do for proc files in the past. As a result, unprivileged poll requests that would be supported now get rejected when opening the cgroup pressure file for writing. Remove the cgroup open() check. psi_trigger_create() handles it. Fixes: 519fabc7aaba ("psi: remove 500ms min window size limitation for triggers") Reported-by: Luca Boccassi <bluca@debian.org> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Luca Boccassi <bluca@debian.org> Acked-by: Suren Baghdasaryan <surenb@google.com> Cc: stable@vger.kernel.org # 6.5+ Link: https://lore.kernel.org/r/20231026164114.2488682-1-hannes@cmpxchg.org
-rw-r--r--kernel/cgroup/cgroup.c12
1 files changed, 0 insertions, 12 deletions
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 1d5b9de3b1b9..4b9ff41ca603 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -3885,14 +3885,6 @@ static __poll_t cgroup_pressure_poll(struct kernfs_open_file *of,
return psi_trigger_poll(&ctx->psi.trigger, of->file, pt);
}
-static int cgroup_pressure_open(struct kernfs_open_file *of)
-{
- if (of->file->f_mode & FMODE_WRITE && !capable(CAP_SYS_RESOURCE))
- return -EPERM;
-
- return 0;
-}
-
static void cgroup_pressure_release(struct kernfs_open_file *of)
{
struct cgroup_file_ctx *ctx = of->priv;
@@ -5299,7 +5291,6 @@ static struct cftype cgroup_psi_files[] = {
{
.name = "io.pressure",
.file_offset = offsetof(struct cgroup, psi_files[PSI_IO]),
- .open = cgroup_pressure_open,
.seq_show = cgroup_io_pressure_show,
.write = cgroup_io_pressure_write,
.poll = cgroup_pressure_poll,
@@ -5308,7 +5299,6 @@ static struct cftype cgroup_psi_files[] = {
{
.name = "memory.pressure",
.file_offset = offsetof(struct cgroup, psi_files[PSI_MEM]),
- .open = cgroup_pressure_open,
.seq_show = cgroup_memory_pressure_show,
.write = cgroup_memory_pressure_write,
.poll = cgroup_pressure_poll,
@@ -5317,7 +5307,6 @@ static struct cftype cgroup_psi_files[] = {
{
.name = "cpu.pressure",
.file_offset = offsetof(struct cgroup, psi_files[PSI_CPU]),
- .open = cgroup_pressure_open,
.seq_show = cgroup_cpu_pressure_show,
.write = cgroup_cpu_pressure_write,
.poll = cgroup_pressure_poll,
@@ -5327,7 +5316,6 @@ static struct cftype cgroup_psi_files[] = {
{
.name = "irq.pressure",
.file_offset = offsetof(struct cgroup, psi_files[PSI_IRQ]),
- .open = cgroup_pressure_open,
.seq_show = cgroup_irq_pressure_show,
.write = cgroup_irq_pressure_write,
.poll = cgroup_pressure_poll,