FAILED: patch "[PATCH] selinux: enable use of both GFP_KERNEL and GFP_ATOMIC in" failed to apply to 5.4-stable tree

The patch below does not apply to the 5.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

Possible dependencies:

abe3c631447d ("selinux: enable use of both GFP_KERNEL and GFP_ATOMIC in convert_context()") d97bd23c2d7d ("selinux: cache the SID -> context string translation") 66f8e2f03c02 ("selinux: sidtab reverse lookup hash table")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From abe3c631447dcd1ba7af972fe6f054bee6f136fa Mon Sep 17 00:00:00 2001
From: "GONG, Ruiqi" <[email protected]>
Date: Wed, 19 Oct 2022 10:57:10 +0800
Subject: [PATCH] selinux: enable use of both GFP_KERNEL and GFP_ATOMIC in
convert_context()

The following warning was triggered on a hardware environment:

SELinux: Converting 162 SID table entries...

  BUG: sleeping function called from invalid context at
       __might_sleep+0x60/0x74 0x0
  in_atomic(): 1, irqs_disabled(): 128, non_block: 0, pid: 5943, name: tar
  CPU: 7 PID: 5943 Comm: tar Tainted: P O 5.10.0 #1
  Call trace:
   dump_backtrace+0x0/0x1c8
   show_stack+0x18/0x28
   dump_stack+0xe8/0x15c
   ___might_sleep+0x168/0x17c
   __might_sleep+0x60/0x74
   __kmalloc_track_caller+0xa0/0x7dc
   kstrdup+0x54/0xac
   convert_context+0x48/0x2e4
   sidtab_context_to_sid+0x1c4/0x36c
   security_context_to_sid_core+0x168/0x238
   security_context_to_sid_default+0x14/0x24
   inode_doinit_use_xattr+0x164/0x1e4
   inode_doinit_with_dentry+0x1c0/0x488
   selinux_d_instantiate+0x20/0x34
   security_d_instantiate+0x70/0xbc
   d_splice_alias+0x4c/0x3c0
   ext4_lookup+0x1d8/0x200 [ext4]
   __lookup_slow+0x12c/0x1e4
   walk_component+0x100/0x200
   path_lookupat+0x88/0x118
   filename_lookup+0x98/0x130
   user_path_at_empty+0x48/0x60
   vfs_statx+0x84/0x140
   vfs_fstatat+0x20/0x30
   __se_sys_newfstatat+0x30/0x74
   __arm64_sys_newfstatat+0x1c/0x2c
   el0_svc_common.constprop.0+0x100/0x184
   do_el0_svc+0x1c/0x2c
   el0_svc+0x20/0x34
   el0_sync_handler+0x80/0x17c
   el0_sync+0x13c/0x140
  SELinux: Context system_u:object_r:pssp_rsyslog_log_t:s0:c0 is
           not valid (left unmapped).

It was found that within a critical section of spin_lock_irqsave in sidtab_context_to_sid(), convert_context() (hooked by sidtab_convert_params.func) might cause the process to sleep via allocating memory with GFP_KERNEL, which is problematic.

As Ondrej pointed out [1], convert_context()/sidtab_convert_params.func has another caller sidtab_convert_tree(), which is okay with GFP_KERNEL. Therefore, fix this problem by adding a gfp_t argument for convert_context()/sidtab_convert_params.func and pass GFP_KERNEL/_ATOMIC properly in individual callers.

index fe5fcf571c56..64a6a37dc36d 100644
@@ -2022,7 +2022,8 @@ static inline int convert_context_handle_invalid_context(
  * in `newc'.  Verify that the context is valid
  * under the new policy.
  */
-static int convert_context(struct context *oldc, struct context *newc, void *p)
+static int convert_context(struct context *oldc, struct context *newc, void *p,
+			   gfp_t gfp_flags)
 {
 	struct convert_context_args *args;
 	struct ocontext *oc;

@@ -2036,7 +2037,7 @@ static int convert_context(struct context *oldc, struct context *newc, void *p)
 	args = p;
 
 	if (oldc->str) {
-		s = kstrdup(oldc->str, GFP_KERNEL);
+		s = kstrdup(oldc->str, gfp_flags);
 		if (!s)
 			return -ENOMEM;
 

index a54b8652bfb5..db5cce385bf8 100644
@@ -325,7 +325,7 @@ int sidtab_context_to_sid(struct sidtab *s, struct context *context,
 		}
 
 		rc = convert->func(context, &dst_convert->context,
-				   convert->args);
+				   convert->args, GFP_ATOMIC);
 		if (rc) {
 			context_destroy(&dst->context);
 			goto out_unlock;

@@ -404,7 +404,7 @@ static int sidtab_convert_tree(union sidtab_entry_inner *edst,
 		while (i < SIDTAB_LEAF_ENTRIES && *pos < count) {
 			rc = convert->func(&esrc->ptr_leaf->entries[i].context,
 					   &edst->ptr_leaf->entries[i].context,
-					   convert->args);
+					   convert->args, GFP_KERNEL);
 			if (rc)
 				return rc;
 			(*pos)++;

index 4eff0e49dcb2..9fce0d553fe2 100644
@@ -65,7 +65,7 @@ struct sidtab_isid_entry {
 };
 
 struct sidtab_convert_params {
-	int (*func)(struct context *oldc, struct context *newc, void *args);
+	int (*func)(struct context *oldc, struct context *newc, void *args, gfp_t gfp_flags);
 	void *args;
 	struct sidtab *target;
 };