[PATCH 6.19 795/844] procfs: fix possible double mmput() in do_procmap_query()

[Sasha Levin]

From: Andrii Nakryiko <andrii@xxxxxxxxxx>

[ Upstream commit 61dc9f776705d6db6847c101b98fa4f0e9eb6fa3 ]

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@xxxxxxxxxx
Fixes: b5cbacd7f86f ("procfs: avoid fetching build ID while holding VMA lock")
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
Reported-by: Ruikai Peng <ruikai@xxxxxxx>
Reported-by: Thomas Gleixner <tglx@xxxxxxxxxx>
Tested-by: Thomas Gleixner <tglx@xxxxxxxxxx>
Reviewed-by: Shakeel Butt <shakeel.butt@xxxxxxxxx>
Reported-by: syzbot+237b5b985b78c1da9600@xxxxxxxxxxxxxxxxxxxxxxxxx
Cc: Ruikai Peng <ruikai@xxxxxxx>
Closes: https://lkml.kernel.org/r/CAFD3drOJANTZPuyiqMdqpiRwOKnHwv5QgMNZghCDr-WxdiHvMg@xxxxxxxxxxxxxx
Closes: https://lore.kernel.org/all/698aaf3c.050a0220.3b3015.0088.GAE@xxxxxxxxxx/T/#u
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 fs/proc/task_mmu.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 26188a4ad1abd..2f55efc368162 100644
--- 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);
-- 
2.51.0