Commit ca680185 authored Oct 19, 2022 by GONG, Ruiqi Committed by Lee Jones Jan 23, 2024

BACKPORT: 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.

Bug: 254441685
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/20221018120111.1474581-1-gongruiqi1@huawei.com/

 [1]
Reported-by: Tan Ninghao <tanninghao1@huawei.com>
Fixes: ee1a84fdfeed ("selinux: overhaul sidtab to fix bug and improve performance")
Signed-off-by: GONG, Ruiqi <gongruiqi1@huawei.com>
Reviewed-by: Ondrej Mosnacek <omosnace@redhat.com>
[PM: wrap long BUG() output lines, tweak subject line]
Signed-off-by: Paul Moore <paul@paul-moore.com>
(cherry picked from commit abe3c631447dcd1ba7af972fe6f054bee6f136fa)
[Lee: Trivial white-space differences]
Signed-off-by: Lee Jones <joneslee@google.com>
Change-Id: Id5d763b0e858d917629c95005ce982d421a3f54f

parent 6500084f

security/selinux/ss/services.c

+3 −2

Original line number	Diff line number	Diff line
		@@ -1966,7 +1966,8 @@ struct convert_context_args {
		* 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;
		@@ -1980,7 +1981,7 @@ 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;

security/selinux/ss/sidtab.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -289,7 +289,7 @@ 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;
		@@ -368,7 +368,7 @@ 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)++;

security/selinux/ss/sidtab.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -64,7 +64,7 @@ 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;
		};