From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1792832538; b=y8+r3m7tzw9XSZ7vnl3tWvacXkCZ2qe+LPboUBff4LLZAhFDlao+XEFmmQp6b+4yKon+ TrHJinYeRIgaNA2jYFNl1jw5t0LDYx8190pd33ZNJguXAwebMA08I1t4c5sWBlfPPqA8o ek0hrp7za74aMe3kLitRY+VLbxwLJFuavPex0LLZJBKzllxD2KaZ4hIaAl+pyAKpt/0xU wtfAUTL6zDIrZLEH48kBRm7yxc45mi7gPAupTi/Hoqxz6AkR2hoLf0dCBdnsidn5eefQq mbf6SuTh/Ucg0G3bcDdqOLaV+4odEK8aw391Dg2Oaj5Orbdy9rirE/N6aUz54WHNGlQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792832538; h=Received:DKIM-Signature:Date:To:From:Subject:Message-Id; bh=gAsP5gtCLYqP7yWzios0wBdxc68jHD/QOc1Ds0GWkZk=; b=dz2nn/d1ptEKr4b370iw6E9LBNB3KlNBsKg45p8/lUCjgHcmOzCjHuo3aaF2LlU8BMVI aAFoS4j/FlOcLf+GrvNMrSFKU5TRIdtNJo9swuRS4QZboHNLsUiYRTVkcOkBRAW0GpwUd b0CeBILLZa3pz8A2OY5MFtZqkezj05Y+aUimvB2uHD5aHYoMnIkbDryGxK44B9V/1UzPu w15LAzUpKuwzrPPU3mNYl6RBwL2gBGtNBz3h6Tp7zFsAM1A0f1RBq4rlPR6Z2O6pWc5us JxHbxKjk+jt/PL0a6RjUtzeSqBnYxt5ClcUwrwXTMYjI4i/igMZpJacgeQWuABKLy9w== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linux-foundation.org header.i=@linux-foundation.org header.a=rsa-sha256 header.s=korg header.b=SXrdVcGd; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F2F5B606A31D; Sat, 24 Oct 2026 09:02:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linux-foundation.org header.i=@linux-foundation.org header.a=rsa-sha256 header.s=korg header.b=SXrdVcGd Received: by smtp.kernel.org (Postfix) with ESMTPSA id BC29A1F01825; Sat, 24 Oct 2026 09:02:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1792832537; bh=gAsP5gtCLYqP7yWzios0wBdxc68jHD/QOc1Ds0GWkZk=; h=Date:To:From:Subject; b=SXrdVcGd7xC0H4Qtenr9FWhu+tyVU/3KR8xyNc5HispnI65OqH7CbSniZXeYXWy4w Xt9VjXw92XbU3ee01yUOrN2qhB3PtykSYuc45hX+JXrkWLAY7MufHkVic4tHs3dS0U AFjt316Ka12o2LyLEFUDChWJvPqRgkJvgkEA5nN0= Date: Sat, 24 Oct 2026 02:02:17 -0700 To: mm-commits@vger.kernel.org,vbabka@kernel.org,usama.anjum@arm.com,stable@vger.kernel.org,pfalcato@suse.de,ljs@kernel.org,liam@infradead.org,jannh@google.com,ngocquy0700@gmail.com,akpm@linux-foundation.org From: Andrew Morton Subject: [merged mm-stable] fs-proc-task_mmu-pin-mm_users-in-do_pagemap_scan.patch removed from -mm tree Message-Id: <20261024090217.BC29A1F01825@smtp.kernel.org> X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list The quilt patch titled Subject: fs/proc/task_mmu: pin mm_users in do_pagemap_scan() has been removed from the -mm tree. Its filename was fs-proc-task_mmu-pin-mm_users-in-do_pagemap_scan.patch This patch was dropped because it was merged into the mm-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: Ngoc Quy Subject: fs/proc/task_mmu: pin mm_users in do_pagemap_scan() Date: Wed, 14 Oct 2026 16:55:40 +0700 The PAGEMAP_SCAN ioctl takes mmap_read_lock() on an mm obtained from /proc//pagemap without holding a reference to mm_users. proc_mem_open() deliberately grabs only mm_count, so a consumer that touches the address space has to call mmget_not_zero() first. Every other consumer in this file does -- m_start(), do_procmap_query(), show_smaps_rollup() and pagemap_read() -- but do_pagemap_scan() does not. Without that reference the target can reach exit_mmap() concurrently, and exit_mmap() calls unmap_vmas() while holding mmap_lock only for reading, which does not exclude the scanner. For ordinary VMAs this is harmless, as free_pgtables() and remove_vma() run afterwards under mmap_write_lock. A shared hugetlb VMA is different: __hugetlb_zap_end() frees the VMA's hugetlb_vma_lock inside the read-locked phase. walk_hugetlb_range() can therefore load vma->vm_private_data, have the lock freed underneath it, and then down_read() a freed rw_semaphore. The load happens before the freeing side clears the pointer, so this is a use-after-free and not a NULL dereference. Any unprivileged user can reach it with no huge pages configured, as hugetlb_reserve_pages() allocates the lock before the VM_NORESERVE early return. Pin mm_users across the scan, the way the other consumers do. mmput() from the exiting task can then no longer reach exit_mmap() while a walk is in progress. [akpm@linux-foundation.org: remove unneeded & undesirable test for !mm] Link: https://lore.kernel.org/20261014095540.3261469-1-ngocquy0700@gmail.com Fixes: 52526ca7fdb9 ("fs/proc/task_mmu: implement IOCTL to get and optionally clear info about PTEs") Signed-off-by: Ngoc Quy Signed-off-by: Andrew Morton Assisted-by: Claude:claude-opus-5 Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Vlastimil Babka Cc: Jann Horn Cc: Pedro Falcato Cc: Muhammad Usama Anjum Cc: --- fs/proc/task_mmu.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) --- a/fs/proc/task_mmu.c~fs-proc-task_mmu-pin-mm_users-in-do_pagemap_scan +++ a/fs/proc/task_mmu.c @@ -3120,15 +3120,18 @@ static long do_pagemap_scan(struct mm_st size_t n_ranges_out = 0; int ret; + if (!mmget_not_zero(mm)) + return -ESRCH; + ret = pagemap_scan_get_args(&p.arg, uarg); if (ret) - return ret; + goto out_mmput; p.masks_of_interest = p.arg.category_mask | p.arg.category_anyof_mask | p.arg.return_mask; ret = pagemap_scan_init_bounce_buffer(&p); if (ret) - return ret; + goto out_mmput; for (walk_start = p.arg.start; walk_start < p.arg.end; walk_start = p.arg.walk_end) { @@ -3183,6 +3186,8 @@ static long do_pagemap_scan(struct mm_st ret = -EFAULT; kfree(p.vec_buf); +out_mmput: + mmput(mm); return ret; } _ Patches currently in -mm which might be from ngocquy0700@gmail.com are