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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.

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: ee1a84fdfe ("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>
This commit is contained in:
GONG, Ruiqi 2022-10-19 10:57:10 +08:00 committed by Paul Moore
parent 9abf2313ad
commit abe3c63144
3 changed files with 6 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
security/selinux/ss/services.c
View File

@ -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;

4
security/selinux/ss/sidtab.c
View File

@ -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)++;

2
security/selinux/ss/sidtab.h
View File

@ -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;
};