procfs: fix possible double mmput() in do_procmap_query()

When user provides incorrectly sized buffer for build ID for PROCMAP_QUERY
we return with -ENAMETOOLONG error.  After recent changes this condition
happens later, after we unlocked mmap_lock/per-VMA lock and did mmput(),
so original goto out is now wrong and will double-mmput() mm_struct.  Fix
by jumping further to clean up only vm_file and name_buf.

Link: https://lkml.kernel.org/r/20260210192738.3041609-1-andrii@kernel.org
Fixes: b5cbacd7f86f ("procfs: avoid fetching build ID while holding VMA lock")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Reported-by: Ruikai Peng <ruikai@pwno.io>
Reported-by: Thomas Gleixner <tglx@kernel.org>
Tested-by: Thomas Gleixner <tglx@kernel.org>
Reviewed-by: Shakeel Butt <shakeel.butt@linux.dev>
Reported-by: syzbot+237b5b985b78c1da9600@syzkaller.appspotmail.com
Cc: Ruikai Peng <ruikai@pwno.io>
Closes: https://lkml.kernel.org/r/CAFD3drOJANTZPuyiqMdqpiRwOKnHwv5QgMNZghCDr-WxdiHvMg@mail.gmail.com
Closes: https://lore.kernel.org/all/698aaf3c.050a0220.3b3015.0088.GAE@google.com/T/#u
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 26188a4ad1abd9de3828b8dceb816c30a06291cc..2f55efc368162d55e1dc13f3e301cfcc807536c7 100644 (file)
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -780,7 +780,7 @@ static int do_procmap_query(struct mm_struct *mm, void __user *uarg)
                } else {
                        if (karg.build_id_size < build_id_sz) {
                                err = -ENAMETOOLONG;
-                               goto out;
+                               goto out_file;
                        }
                        karg.build_id_size = build_id_sz;
                }
@@ -808,6 +808,7 @@ static int do_procmap_query(struct mm_struct *mm, void __user *uarg)
 out:
        query_vma_teardown(&lock_ctx);
        mmput(mm);
+out_file:
        if (vm_file)
                fput(vm_file);
        kfree(name_buf);