[PATCH] mm/mempolicy: Fix exception handling in shared_policy_replace()

[Markus Elfring <Markus.Elfring@xxxxxx>]

Date: Thu, 23 Mar 2023 18:18:59 +0100

The label “err_out” was used to jump to another pointer check despite of
the detail in the implementation of the function “shared_policy_replace”
that it was determined already that a corresponding variable contained a
null pointer because of a failed call of the function “kmem_cache_alloc”.

1. Use more appropriate labels instead.

2. The implementation of the function “mpol_put” contains a pointer check
   for its single input parameter.
   Thus delete a redundant check in the caller.


This issue was detected by using the Coccinelle software.

Fixes: 42288fe366c4f1ce7522bc9f27d0bc2a81c55264 ("mm: mempolicy: Convert shared_policy mutex to spinlock")
Signed-off-by: Markus Elfring <elfring@xxxxxxxxxxxxxxxxxxxxx>
---
 mm/mempolicy.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index a256a241fd1d..fb0485688dcb 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -2736,13 +2736,12 @@ static int shared_policy_replace(struct shared_policy *sp, unsigned long start,
         sp_insert(sp, new);
     write_unlock(&sp->lock);
     ret = 0;
+put_mpol:
+    mpol_put(mpol_new);
 
-err_out:
-    if (mpol_new)
-        mpol_put(mpol_new);
     if (n_new)
         kmem_cache_free(sn_cache, n_new);
-
+exit:
     return ret;
 
 alloc_new:
@@ -2750,10 +2749,10 @@ static int shared_policy_replace(struct shared_policy *sp, unsigned long start,
     ret = -ENOMEM;
     n_new = kmem_cache_alloc(sn_cache, GFP_KERNEL);
     if (!n_new)
-        goto err_out;
+        goto exit;
     mpol_new = kmem_cache_alloc(policy_cache, GFP_KERNEL);
     if (!mpol_new)
-        goto err_out;
+        goto put_mpol;
     atomic_set(&mpol_new->refcnt, 1);
     goto restart;
 }
--
2.40.0