+ procfs-fix-possible-double-mmput-in-do_procmap_query.patch added to mm-hotfixes-unstable branch

+ procfs-fix-possible-double-mmput-in-do_procmap_query.patch added to mm-hotfixes-unstable branch

[Andrew Morton]

The patch titled
     Subject: procfs: fix possible double mmput() in do_procmap_query()
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     procfs-fix-possible-double-mmput-in-do_procmap_query.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/procfs-fix-possible-double-mmput-in-do_procmap_query.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Andrii Nakryiko <andrii@kernel.org>
Subject: procfs: fix possible double mmput() in do_procmap_query()
Date: Tue, 10 Feb 2026 11:27:38 -0800

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>
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>
---

 fs/proc/task_mmu.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/fs/proc/task_mmu.c~procfs-fix-possible-double-mmput-in-do_procmap_query
+++ a/fs/proc/task_mmu.c
@@ -780,7 +780,7 @@ static int do_procmap_query(struct mm_st
 		} 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_st
 out:
 	query_vma_teardown(&lock_ctx);
 	mmput(mm);
+out_file:
 	if (vm_file)
 		fput(vm_file);
 	kfree(name_buf);
_

Patches currently in -mm which might be from andrii@kernel.org are

procfs-fix-possible-double-mmput-in-do_procmap_query.patch