mlxsw: Various ACL fixes

Ido Schimmel writes:

Fix various problems in the ACL (i.e., flower offload) code. See the commit messages for more details.

Ido Schimmel (9):
mlxsw: spectrum_acl_tcam: Fix race in region ID allocation
mlxsw: spectrum_acl_tcam: Fix race during rehash delayed work
mlxsw: spectrum_acl_tcam: Fix possible use-after-free during activity
update
mlxsw: spectrum_acl_tcam: Fix possible use-after-free during rehash
mlxsw: spectrum_acl_tcam: Rate limit error message
mlxsw: spectrum_acl_tcam: Fix memory leak during rehash
mlxsw: spectrum_acl_tcam: Fix warning during rehash
mlxsw: spectrum_acl_tcam: Fix incorrect list API usage
mlxsw: spectrum_acl_tcam: Fix memory leak when canceling rehash work

 .../mellanox/mlxsw/spectrum_acl_tcam.c        | 115 +++++++++++-------
 .../mellanox/mlxsw/spectrum_acl_tcam.h        |   5 +-
 2 files changed, 75 insertions(+), 45 deletions(-)

2.43.0

From: Ido Schimmel <[email protected]>

Region identifiers can be allocated both when user space tries to insert a new tc filter and when filters are migrated from one region to another as part of the rehash delayed work.

There is no lock protecting the bitmap from which these identifiers are allocated from, which is racy and leads to bad parameter errors from the device's firmware.

Fix by converting the bitmap to IDA which handles its own locking. For consistency, do the same for the group identifiers that are part of the same structure.

---
 .../mellanox/mlxsw/spectrum_acl_tcam.c        | 61 ++++++++-----------
 .../mellanox/mlxsw/spectrum_acl_tcam.h        |  5 +-
 2 files changed, 30 insertions(+), 36 deletions(-)

index f20052776b3f..b6a4652a6475 100644
@@ -10,6 +10,7 @@
 #include <linux/netdevice.h>
 #include <linux/mutex.h>
 #include <linux/refcount.h>
+#include <linux/idr.h>
 #include <net/devlink.h>
 #include <trace/events/mlxsw.h>
 

@@ -58,41 +59,43 @@ int mlxsw_sp_acl_tcam_priority_get(struct mlxsw_sp *mlxsw_sp,
 static int mlxsw_sp_acl_tcam_region_id_get(struct mlxsw_sp_acl_tcam *tcam,
 					   u16 *p_id)
 {
-	u16 id;
+	int id;
 
-	id = find_first_zero_bit(tcam->used_regions, tcam->max_regions);
-	if (id < tcam->max_regions) {
-		__set_bit(id, tcam->used_regions);
-		*p_id = id;
-		return 0;
-	}
-	return -ENOBUFS;
+	id = ida_alloc_max(&tcam->used_regions, tcam->max_regions - 1,
+			   GFP_KERNEL);
+	if (id < 0)
+		return id;
+
+	*p_id = id;
+
+	return 0;
 }
 
 static void mlxsw_sp_acl_tcam_region_id_put(struct mlxsw_sp_acl_tcam *tcam,
 					    u16 id)
 {
-	__clear_bit(id, tcam->used_regions);
+	ida_free(&tcam->used_regions, id);
 }
 
 static int mlxsw_sp_acl_tcam_group_id_get(struct mlxsw_sp_acl_tcam *tcam,
 					  u16 *p_id)
 {
-	u16 id;
+	int id;
 
-	id = find_first_zero_bit(tcam->used_groups, tcam->max_groups);
-	if (id < tcam->max_groups) {
-		__set_bit(id, tcam->used_groups);
-		*p_id = id;
-		return 0;
-	}
-	return -ENOBUFS;
+	id = ida_alloc_max(&tcam->used_groups, tcam->max_groups - 1,
+			   GFP_KERNEL);
+	if (id < 0)
+		return id;
+
+	*p_id = id;
+
+	return 0;
 }
 
 static void mlxsw_sp_acl_tcam_group_id_put(struct mlxsw_sp_acl_tcam *tcam,
 					   u16 id)
 {
-	__clear_bit(id, tcam->used_groups);
+	ida_free(&tcam->used_groups, id);
 }
 
 struct mlxsw_sp_acl_tcam_pattern {

@@ -1549,19 +1552,11 @@ int mlxsw_sp_acl_tcam_init(struct mlxsw_sp *mlxsw_sp,
 	if (max_tcam_regions < max_regions)
 		max_regions = max_tcam_regions;
 
-	tcam->used_regions = bitmap_zalloc(max_regions, GFP_KERNEL);
-	if (!tcam->used_regions) {
-		err = -ENOMEM;
-		goto err_alloc_used_regions;
-	}
+	ida_init(&tcam->used_regions);
 	tcam->max_regions = max_regions;
 
 	max_groups = MLXSW_CORE_RES_GET(mlxsw_sp->core, ACL_MAX_GROUPS);
-	tcam->used_groups = bitmap_zalloc(max_groups, GFP_KERNEL);
-	if (!tcam->used_groups) {
-		err = -ENOMEM;
-		goto err_alloc_used_groups;
-	}
+	ida_init(&tcam->used_groups);
 	tcam->max_groups = max_groups;
 	tcam->max_group_size = MLXSW_CORE_RES_GET(mlxsw_sp->core,
 						  ACL_MAX_GROUP_SIZE);

@@ -1575,10 +1570,8 @@ int mlxsw_sp_acl_tcam_init(struct mlxsw_sp *mlxsw_sp,
 	return 0;
 
 err_tcam_init:
-	bitmap_free(tcam->used_groups);
-err_alloc_used_groups:
-	bitmap_free(tcam->used_regions);
-err_alloc_used_regions:
+	ida_destroy(&tcam->used_groups);
+	ida_destroy(&tcam->used_regions);
 	mlxsw_sp_acl_tcam_rehash_params_unregister(mlxsw_sp);
 err_rehash_params_register:
 	mutex_destroy(&tcam->lock);

@@ -1591,8 +1584,8 @@ void mlxsw_sp_acl_tcam_fini(struct mlxsw_sp *mlxsw_sp,
 	const struct mlxsw_sp_acl_tcam_ops *ops = mlxsw_sp->acl_tcam_ops;
 
 	ops->fini(mlxsw_sp, tcam->priv);
-	bitmap_free(tcam->used_groups);
-	bitmap_free(tcam->used_regions);
+	ida_destroy(&tcam->used_groups);
+	ida_destroy(&tcam->used_regions);
 	mlxsw_sp_acl_tcam_rehash_params_unregister(mlxsw_sp);
 	mutex_destroy(&tcam->lock);
 }

index 462bf448497d..79a1d8606512 100644
@@ -6,15 +6,16 @@
 
 #include <linux/list.h>
 #include <linux/parman.h>
+#include <linux/idr.h>
 
 #include "reg.h"
 #include "spectrum.h"
 #include "core_acl_flex_keys.h"
 
 struct mlxsw_sp_acl_tcam {
-	unsigned long *used_regions; /* bit array */
+	struct ida used_regions;
 	unsigned int max_regions;
-	unsigned long *used_groups;  /* bit array */
+	struct ida used_groups;
 	unsigned int max_groups;
 	unsigned int max_group_size;
 	struct mutex lock; /* guards vregion list */

2.43.0

From: Ido Schimmel <[email protected]>

The purpose of the rehash delayed work is to reduce the number of masks (eRPs) used by an ACL region as the eRP bank is a global and limited resource.

This is done in three steps:

1. Creating a new set of masks and a new ACL region which will use the new masks and to which the existing filters will be migrated to. The new region is assigned to 'vregion->region' and the region from which the filters are migrated from is assigned to 'vregion->region2'.

2. Migrating all the filters from the old region to the new region.

3. Destroying the old region and setting 'vregion->region2' to NULL.

Only the second steps is performed under the 'vregion->lock' mutex although its comments says that among other things it "Protects consistency of region, region2 pointers".

This is problematic as the first step can race with filter insertion from user space that uses 'vregion->region', but under the mutex.

Fix by holding the mutex across the entirety of the delayed work and not only during the second step.

---
 drivers/net/ethernet/mellanox/mlxsw/spectrum_acl_tcam.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

index b6a4652a6475..9c0c728bb42d 100644
@@ -718,7 +718,9 @@ static void mlxsw_sp_acl_tcam_vregion_rehash_work(struct work_struct *work)
 			     rehash.dw.work);
 	int credits = MLXSW_SP_ACL_TCAM_VREGION_REHASH_CREDITS;
 
+	mutex_lock(&vregion->lock);
 	mlxsw_sp_acl_tcam_vregion_rehash(vregion->mlxsw_sp, vregion, &credits);
+	mutex_unlock(&vregion->lock);
 	if (credits < 0)
 		/* Rehash gone out of credits so it was interrupted.
 		 * Schedule the work as soon as possible to continue.

@@ -1323,7 +1325,6 @@ mlxsw_sp_acl_tcam_vregion_migrate(struct mlxsw_sp *mlxsw_sp,
 	int err, err2;
 
 	trace_mlxsw_sp_acl_tcam_vregion_migrate(mlxsw_sp, vregion);
-	mutex_lock(&vregion->lock);
 	err = mlxsw_sp_acl_tcam_vchunk_migrate_all(mlxsw_sp, vregion,
 						   ctx, credits);
 	if (err) {

@@ -1343,7 +1344,6 @@ mlxsw_sp_acl_tcam_vregion_migrate(struct mlxsw_sp *mlxsw_sp,
 			/* Let the rollback to be continued later on. */
 		}
 	}
-	mutex_unlock(&vregion->lock);
 	trace_mlxsw_sp_acl_tcam_vregion_migrate_end(mlxsw_sp, vregion);
 	return err;
 }

2.43.0

From: Ido Schimmel <[email protected]>

The rule activity update delayed work periodically traverses the list of configured rules and queries their activity from the device.

As part of this task it accesses the entry pointed by 'ventry->entry', but this entry can be changed concurrently by the rehash delayed work, leading to a use-after-free [1].

Fix by closing the race and perform the activity query under the 'vregion->lock' mutex.

[1]

BUG: KASAN: slab-use-after-free in mlxsw_sp_acl_tcam_flower_rule_activity_get+0x121/0x140
Read of size 8 at addr ffff8881054ed808 by task kworker/0:18/181

CPU: 0 PID: 181 Comm: kworker/0:18 Not tainted 6.9.0-rc2-custom-00781-gd5ab772d32f7 #2
Hardware name: Mellanox Technologies Ltd. MSN3700/VMOD0005, BIOS 5.11 01/06/2019
Workqueue: mlxsw_core mlxsw_sp_acl_rule_activity_update_work
Call Trace:
 <TASK>
 dump_stack_lvl+0xc6/0x120
 print_report+0xce/0x670
 kasan_report+0xd7/0x110
 mlxsw_sp_acl_tcam_flower_rule_activity_get+0x121/0x140
 mlxsw_sp_acl_rule_activity_update_work+0x219/0x400
 process_one_work+0x8eb/0x19b0
 worker_thread+0x6c9/0xf70
 kthread+0x2c9/0x3b0
 ret_from_fork+0x4d/0x80
 ret_from_fork_asm+0x1a/0x30
 </TASK>

Allocated by task 1039:
 kasan_save_stack+0x33/0x60
 kasan_save_track+0x14/0x30
 __kasan_kmalloc+0x8f/0xa0
 __kmalloc+0x19c/0x360
 mlxsw_sp_acl_tcam_entry_create+0x7b/0x1f0
 mlxsw_sp_acl_tcam_vchunk_migrate_all+0x30d/0xb50
 mlxsw_sp_acl_tcam_vregion_rehash_work+0x157/0x1300
 process_one_work+0x8eb/0x19b0
 worker_thread+0x6c9/0xf70
 kthread+0x2c9/0x3b0
 ret_from_fork+0x4d/0x80
 ret_from_fork_asm+0x1a/0x30

Freed by task 1039:
 kasan_save_stack+0x33/0x60
 kasan_save_track+0x14/0x30
 kasan_save_free_info+0x3b/0x60
 poison_slab_object+0x102/0x170
 __kasan_slab_free+0x14/0x30
 kfree+0xc1/0x290
 mlxsw_sp_acl_tcam_vchunk_migrate_all+0x3d7/0xb50
 mlxsw_sp_acl_tcam_vregion_rehash_work+0x157/0x1300
 process_one_work+0x8eb/0x19b0
 worker_thread+0x6c9/0xf70
 kthread+0x2c9/0x3b0
 ret_from_fork+0x4d/0x80
 ret_from_fork_asm+0x1a/0x30

---
 .../net/ethernet/mellanox/mlxsw/spectrum_acl_tcam.c    | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

index 9c0c728bb42d..7e69225c057d 100644
@@ -1159,8 +1159,14 @@ mlxsw_sp_acl_tcam_ventry_activity_get(struct mlxsw_sp *mlxsw_sp,
 				      struct mlxsw_sp_acl_tcam_ventry *ventry,
 				      bool *activity)
 {
-	return mlxsw_sp_acl_tcam_entry_activity_get(mlxsw_sp,
-						    ventry->entry, activity);
+	struct mlxsw_sp_acl_tcam_vregion *vregion = ventry->vchunk->vregion;
+	int err;
+
+	mutex_lock(&vregion->lock);
+	err = mlxsw_sp_acl_tcam_entry_activity_get(mlxsw_sp, ventry->entry,
+						   activity);
+	mutex_unlock(&vregion->lock);
+	return err;
 }
 
 static int

2.43.0

...

...

From: Ido Schimmel <[email protected]>

The rehash delayed work migrates filters from one region to another according to the number of available credits.

The migrated from region is destroyed at the end of the work if the number of credits is non-negative as the assumption is that this is indicative of migration being complete. This assumption is incorrect as a non-negative number of credits can also be the result of a failed migration.

The destruction of a region that still has filters referencing it can result in a use-after-free [1].

Fix by not destroying the region if migration failed.

[1]

BUG: KASAN: slab-use-after-free in mlxsw_sp_acl_ctcam_region_entry_remove+0x21d/0x230
Read of size 8 at addr ffff8881735319e8 by task kworker/0:31/3858

CPU: 0 PID: 3858 Comm: kworker/0:31 Tainted: G        W          6.9.0-rc2-custom-00782-gf2275c2157d8 #5
Hardware name: Mellanox Technologies Ltd. MSN3700/VMOD0005, BIOS 5.11 01/06/2019
Workqueue: mlxsw_core mlxsw_sp_acl_tcam_vregion_rehash_work
Call Trace:
 <TASK>
 dump_stack_lvl+0xc6/0x120
 print_report+0xce/0x670
 kasan_report+0xd7/0x110
 mlxsw_sp_acl_ctcam_region_entry_remove+0x21d/0x230
 mlxsw_sp_acl_ctcam_entry_del+0x2e/0x70
 mlxsw_sp_acl_atcam_entry_del+0x81/0x210
 mlxsw_sp_acl_tcam_vchunk_migrate_all+0x3cd/0xb50
 mlxsw_sp_acl_tcam_vregion_rehash_work+0x157/0x1300
 process_one_work+0x8eb/0x19b0
 worker_thread+0x6c9/0xf70
 kthread+0x2c9/0x3b0
 ret_from_fork+0x4d/0x80
 ret_from_fork_asm+0x1a/0x30
 </TASK>

Allocated by task 174:
 kasan_save_stack+0x33/0x60
 kasan_save_track+0x14/0x30
 __kasan_kmalloc+0x8f/0xa0
 __kmalloc+0x19c/0x360
 mlxsw_sp_acl_tcam_region_create+0xdf/0x9c0
 mlxsw_sp_acl_tcam_vregion_rehash_work+0x954/0x1300
 process_one_work+0x8eb/0x19b0
 worker_thread+0x6c9/0xf70
 kthread+0x2c9/0x3b0
 ret_from_fork+0x4d/0x80
 ret_from_fork_asm+0x1a/0x30

Freed by task 7:
 kasan_save_stack+0x33/0x60
 kasan_save_track+0x14/0x30
 kasan_save_free_info+0x3b/0x60
 poison_slab_object+0x102/0x170
 __kasan_slab_free+0x14/0x30
 kfree+0xc1/0x290
 mlxsw_sp_acl_tcam_region_destroy+0x272/0x310
 mlxsw_sp_acl_tcam_vregion_rehash_work+0x731/0x1300
 process_one_work+0x8eb/0x19b0
 worker_thread+0x6c9/0xf70
 kthread+0x2c9/0x3b0
 ret_from_fork+0x4d/0x80
 ret_from_fork_asm+0x1a/0x30

---
 drivers/net/ethernet/mellanox/mlxsw/spectrum_acl_tcam.c | 1 +
 1 file changed, 1 insertion(+)

index 7e69225c057d..1ff0b2c7c11d 100644
@@ -1451,6 +1451,7 @@ mlxsw_sp_acl_tcam_vregion_rehash(struct mlxsw_sp *mlxsw_sp,
 						ctx, credits);
 	if (err) {
 		dev_err(mlxsw_sp->bus_info->dev, "Failed to migrate vregion\n");
+		return;
 	}
 
 	if (*credits >= 0)

2.43.0

...

...

From: Ido Schimmel <[email protected]>

In the rare cases when the device resources are exhausted it is likely that the rehash delayed work will fail. An error message will be printed whenever this happens which can be overwhelming considering the fact that the work is per-region and that there can be hundreds of regions.

Fix by rate limiting the error message.

---
 drivers/net/ethernet/mellanox/mlxsw/spectrum_acl_tcam.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index 1ff0b2c7c11d..568ae7092fe0 100644
@@ -1450,7 +1450,7 @@ mlxsw_sp_acl_tcam_vregion_rehash(struct mlxsw_sp *mlxsw_sp,
 	err = mlxsw_sp_acl_tcam_vregion_migrate(mlxsw_sp, vregion,
 						ctx, credits);
 	if (err) {
-		dev_err(mlxsw_sp->bus_info->dev, "Failed to migrate vregion\n");
+		dev_err_ratelimited(mlxsw_sp->bus_info->dev, "Failed to migrate vregion\n");
 		return;
 	}
 

2.43.0

From: Ido Schimmel <[email protected]>

The rehash delayed work migrates filters from one region to another. This is done by iterating over all chunks (all the filters with the same priority) in the region and in each chunk iterating over all the filters.

If the migration fails, the code tries to migrate the filters back to the old region. However, the rollback itself can also fail in which case another migration will be erroneously performed. Besides the fact that this ping pong is not a very good idea, it also creates a problem.

Each virtual chunk references two chunks: The currently used one ('vchunk->chunk') and a backup ('vchunk->chunk2'). During migration the first holds the chunk we want to migrate filters to and the second holds the chunk we are migrating filters from.

The code currently assumes - but does not verify - that the backup chunk does not exist (NULL) if the currently used chunk does not reference the target region. This assumption breaks when we are trying to rollback a rollback, resulting in the backup chunk being overwritten and leaked [1].

Fix by not rolling back a failed rollback and add a warning to avoid future cases.

[1]

WARNING: CPU: 5 PID: 1063 at lib/parman.c:291 parman_destroy+0x17/0x20
Modules linked in:
CPU: 5 PID: 1063 Comm: kworker/5:11 Tainted: G        W          6.9.0-rc2-custom-00784-gc6a05c468a0b #14
Hardware name: Mellanox Technologies Ltd. MSN3700/VMOD0005, BIOS 5.11 01/06/2019
Workqueue: mlxsw_core mlxsw_sp_acl_tcam_vregion_rehash_work
RIP: 0010:parman_destroy+0x17/0x20
[...]
Call Trace:
 <TASK>
 mlxsw_sp_acl_atcam_region_fini+0x19/0x60
 mlxsw_sp_acl_tcam_region_destroy+0x49/0xf0
 mlxsw_sp_acl_tcam_vregion_rehash_work+0x1f1/0x470
 process_one_work+0x151/0x370
 worker_thread+0x2cb/0x3e0
 kthread+0xd0/0x100
 ret_from_fork+0x34/0x50
 ret_from_fork_asm+0x1a/0x30
 </TASK>

---
 drivers/net/ethernet/mellanox/mlxsw/spectrum_acl_tcam.c | 4 ++++
 1 file changed, 4 insertions(+)

index 568ae7092fe0..0902eb7651e1 100644
@@ -1200,6 +1200,8 @@ mlxsw_sp_acl_tcam_vchunk_migrate_start(struct mlxsw_sp *mlxsw_sp,
 {
 	struct mlxsw_sp_acl_tcam_chunk *new_chunk;
 
+	WARN_ON(vchunk->chunk2);
+
 	new_chunk = mlxsw_sp_acl_tcam_chunk_create(mlxsw_sp, vchunk, region);
 	if (IS_ERR(new_chunk))
 		return PTR_ERR(new_chunk);

@@ -1334,6 +1336,8 @@ mlxsw_sp_acl_tcam_vregion_migrate(struct mlxsw_sp *mlxsw_sp,
 	err = mlxsw_sp_acl_tcam_vchunk_migrate_all(mlxsw_sp, vregion,
 						   ctx, credits);
 	if (err) {
+		if (ctx->this_is_rollback)
+			return err;
 		/* In case migration was not successful, we need to swap
 		 * so the original region pointer is assigned again
 		 * to vregion->region.

2.43.0

...

From: Ido Schimmel <[email protected]>

As previously explained, the rehash delayed work migrates filters from one region to another. This is done by iterating over all chunks (all the filters with the same priority) in the region and in each chunk iterating over all the filters.

When the work runs out of credits it stores the current chunk and entry as markers in the per-work context so that it would know where to resume the migration from the next time the work is scheduled.

Upon error, the chunk marker is reset to NULL, but without resetting the entry markers despite being relative to it. This can result in migration being resumed from an entry that does not belong to the chunk being migrated. In turn, this will eventually lead to a chunk being iterated over as if it is an entry. Because of how the two structures happen to be defined, this does not lead to KASAN splats, but to warnings such as [1].

Fix by creating a helper that resets all the markers and call it from all the places the currently only reset the chunk marker. For good measures also call it when starting a completely new rehash. Add a warning to avoid future cases.

[1]

WARNING: CPU: 7 PID: 1076 at drivers/net/ethernet/mellanox/mlxsw/core_acl_flex_keys.c:407 mlxsw_afk_encode+0x242/0x2f0
Modules linked in:
CPU: 7 PID: 1076 Comm: kworker/7:24 Tainted: G        W          6.9.0-rc3-custom-00880-g29e61d91b77b #29
Hardware name: Mellanox Technologies Ltd. MSN3700/VMOD0005, BIOS 5.11 01/06/2019
Workqueue: mlxsw_core mlxsw_sp_acl_tcam_vregion_rehash_work
RIP: 0010:mlxsw_afk_encode+0x242/0x2f0
[...]
Call Trace:
 <TASK>
 mlxsw_sp_acl_atcam_entry_add+0xd9/0x3c0
 mlxsw_sp_acl_tcam_entry_create+0x5e/0xa0
 mlxsw_sp_acl_tcam_vchunk_migrate_all+0x109/0x290
 mlxsw_sp_acl_tcam_vregion_rehash_work+0x6c/0x470
 process_one_work+0x151/0x370
 worker_thread+0x2cb/0x3e0
 kthread+0xd0/0x100
 ret_from_fork+0x34/0x50
 </TASK>

---
 .../mellanox/mlxsw/spectrum_acl_tcam.c        | 20 ++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

index 0902eb7651e1..e8c607886621 100644
@@ -730,6 +730,17 @@ static void mlxsw_sp_acl_tcam_vregion_rehash_work(struct work_struct *work)
 		mlxsw_sp_acl_tcam_vregion_rehash_work_schedule(vregion);
 }
 
+static void
+mlxsw_sp_acl_tcam_rehash_ctx_vchunk_reset(struct mlxsw_sp_acl_tcam_rehash_ctx *ctx)
+{
+	/* The entry markers are relative to the current chunk and therefore
+	 * needs to be reset together with the chunk marker.
+	 */
+	ctx->current_vchunk = NULL;
+	ctx->start_ventry = NULL;
+	ctx->stop_ventry = NULL;
+}
+
 static void
 mlxsw_sp_acl_tcam_rehash_ctx_vchunk_changed(struct mlxsw_sp_acl_tcam_vchunk *vchunk)
 {

@@ -752,7 +763,7 @@ mlxsw_sp_acl_tcam_rehash_ctx_vregion_changed(struct mlxsw_sp_acl_tcam_vregion *v
 	 * the current chunk pointer to make sure all chunks
 	 * are properly migrated.
 	 */
-	vregion->rehash.ctx.current_vchunk = NULL;
+	mlxsw_sp_acl_tcam_rehash_ctx_vchunk_reset(&vregion->rehash.ctx);
 }
 
 static struct mlxsw_sp_acl_tcam_vregion *

@@ -1220,7 +1231,7 @@ mlxsw_sp_acl_tcam_vchunk_migrate_end(struct mlxsw_sp *mlxsw_sp,
 {
 	mlxsw_sp_acl_tcam_chunk_destroy(mlxsw_sp, vchunk->chunk2);
 	vchunk->chunk2 = NULL;
-	ctx->current_vchunk = NULL;
+	mlxsw_sp_acl_tcam_rehash_ctx_vchunk_reset(ctx);
 }
 
 static int

@@ -1252,6 +1263,8 @@ mlxsw_sp_acl_tcam_vchunk_migrate_one(struct mlxsw_sp *mlxsw_sp,
 		ventry = list_first_entry(&vchunk->ventry_list,
 					  typeof(*ventry), list);
 
+	WARN_ON(ventry->vchunk != vchunk);
+
 	list_for_each_entry_from(ventry, &vchunk->ventry_list, list) {
 		/* During rollback, once we reach the ventry that failed
 		 * to migrate, we are done.

@@ -1343,7 +1356,7 @@ mlxsw_sp_acl_tcam_vregion_migrate(struct mlxsw_sp *mlxsw_sp,
 		 * to vregion->region.
 		 */
 		swap(vregion->region, vregion->region2);
-		ctx->current_vchunk = NULL;
+		mlxsw_sp_acl_tcam_rehash_ctx_vchunk_reset(ctx);
 		ctx->this_is_rollback = true;
 		err2 = mlxsw_sp_acl_tcam_vchunk_migrate_all(mlxsw_sp, vregion,
 							    ctx, credits);

@@ -1402,6 +1415,7 @@ mlxsw_sp_acl_tcam_vregion_rehash_start(struct mlxsw_sp *mlxsw_sp,
 
 	ctx->hints_priv = hints_priv;
 	ctx->this_is_rollback = false;
+	mlxsw_sp_acl_tcam_rehash_ctx_vchunk_reset(ctx);
 
 	return 0;
 

2.43.0

From: Ido Schimmel <[email protected]>

Both the function that migrates all the chunks within a region and the function that migrates all the entries within a chunk call list_first_entry() on the respective lists without checking that the lists are not empty. This is incorrect usage of the API, which leads to the following warning [1].

Fix by returning if the lists are empty as there is nothing to migrate in this case.

[1]

WARNING: CPU: 0 PID: 6437 at drivers/net/ethernet/mellanox/mlxsw/spectrum_acl_tcam.c:1266 mlxsw_sp_acl_tcam_vchunk_migrate_all+0x1f1/0>
Modules linked in:
CPU: 0 PID: 6437 Comm: kworker/0:37 Not tainted 6.9.0-rc3-custom-00883-g94a65f079ef6 #39
Hardware name: Mellanox Technologies Ltd. MSN3700/VMOD0005, BIOS 5.11 01/06/2019
Workqueue: mlxsw_core mlxsw_sp_acl_tcam_vregion_rehash_work
RIP: 0010:mlxsw_sp_acl_tcam_vchunk_migrate_all+0x1f1/0x2c0
[...]
Call Trace:
 <TASK>
 mlxsw_sp_acl_tcam_vregion_rehash_work+0x6c/0x4a0
 process_one_work+0x151/0x370
 worker_thread+0x2cb/0x3e0
 kthread+0xd0/0x100
 ret_from_fork+0x34/0x50
 ret_from_fork_asm+0x1a/0x30
 </TASK>

---
 drivers/net/ethernet/mellanox/mlxsw/spectrum_acl_tcam.c | 7 +++++++
 1 file changed, 7 insertions(+)

index e8c607886621..89a5ebc3463f 100644
@@ -1254,6 +1254,9 @@ mlxsw_sp_acl_tcam_vchunk_migrate_one(struct mlxsw_sp *mlxsw_sp,
 		return 0;
 	}
 
+	if (list_empty(&vchunk->ventry_list))
+		goto out;
+
 	/* If the migration got interrupted, we have the ventry to start from
 	 * stored in context.
 	 */

@@ -1305,6 +1308,7 @@ mlxsw_sp_acl_tcam_vchunk_migrate_one(struct mlxsw_sp *mlxsw_sp,
 		}
 	}
 
+out:
 	mlxsw_sp_acl_tcam_vchunk_migrate_end(mlxsw_sp, vchunk, ctx);
 	return 0;
 }

@@ -1318,6 +1322,9 @@ mlxsw_sp_acl_tcam_vchunk_migrate_all(struct mlxsw_sp *mlxsw_sp,
 	struct mlxsw_sp_acl_tcam_vchunk *vchunk;
 	int err;
 
+	if (list_empty(&vregion->vchunk_list))
+		return 0;
+
 	/* If the migration got interrupted, we have the vchunk
 	 * we are working on stored in context.
 	 */

2.43.0

From: Ido Schimmel <[email protected]>

The rehash delayed work is rescheduled with a delay if the number of credits at end of the work is not negative as supposedly it means that the migration ended. Otherwise, it is rescheduled immediately.

After "mlxsw: spectrum_acl_tcam: Fix possible use-after-free during rehash" the above is no longer accurate as a non-negative number of credits is no longer indicative of the migration being done. It can also happen if the work encountered an error in which case the migration will resume the next time the work is scheduled.

The significance of the above is that it is possible for the work to be pending and associated with hints that were allocated when the migration started. This leads to the hints being leaked [1] when the work is canceled while pending as part of ACL region dismantle.

Fix by freeing the hints if hints are associated with a work that was canceled while pending.

Blame the original commit since the reliance on not having a pending work associated with hints is fragile.

[1]
unreferenced object 0xffff88810e7c3000 (size 256):
comm "kworker/0:16", pid 176, jiffies 4295460353 hex dump (first 32 bytes):

    00 30 95 11 81 88 ff ff 61 00 00 00 00 00 00 80  .0......a.......
    00 00 61 00 40 00 00 00 00 00 00 00 04 00 00 00  ..a.@...........
  backtrace (crc 2544ddb9):
    [<00000000cf8cfab3>] kmalloc_trace+0x23f/0x2a0
    [<000000004d9a1ad9>] objagg_hints_get+0x42/0x390
    [<000000000b143cf3>] mlxsw_sp_acl_erp_rehash_hints_get+0xca/0x400
    [<0000000059bdb60a>] mlxsw_sp_acl_tcam_vregion_rehash_work+0x868/0x1160
    [<00000000e81fd734>] process_one_work+0x59c/0xf20
    [<00000000ceee9e81>] worker_thread+0x799/0x12c0
    [<00000000bda6fe39>] kthread+0x246/0x300
    [<0000000070056d23>] ret_from_fork+0x34/0x70
    [<00000000dea2b93e>] ret_from_fork_asm+0x1a/0x30

---
 drivers/net/ethernet/mellanox/mlxsw/spectrum_acl_tcam.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

index 89a5ebc3463f..92a406f02eae 100644
@@ -836,10 +836,14 @@ mlxsw_sp_acl_tcam_vregion_destroy(struct mlxsw_sp *mlxsw_sp,
 	struct mlxsw_sp_acl_tcam *tcam = vregion->tcam;
 
 	if (vgroup->vregion_rehash_enabled && ops->region_rehash_hints_get) {
+		struct mlxsw_sp_acl_tcam_rehash_ctx *ctx = &vregion->rehash.ctx;
+
 		mutex_lock(&tcam->lock);
 		list_del(&vregion->tlist);
 		mutex_unlock(&tcam->lock);
-		cancel_delayed_work_sync(&vregion->rehash.dw);
+		if (cancel_delayed_work_sync(&vregion->rehash.dw) &&
+		    ctx->hints_priv)
+			ops->region_rehash_hints_put(ctx->hints_priv);
 	}
 	mlxsw_sp_acl_tcam_vgroup_vregion_detach(mlxsw_sp, vregion);
 	if (vregion->region2)

2.43.0