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Thu, 22 May 2025 11:50:48 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id p+hqB5gPL2izYwAAD6G6ig (envelope-from ); Thu, 22 May 2025 11:50:48 +0000 Date: Thu, 22 May 2025 13:50:46 +0200 From: Oscar Salvador To: yangge1116@126.com Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, 21cnbao@gmail.com, david@redhat.com, baolin.wang@linux.alibaba.com, muchun.song@linux.dev, liuzixing@hygon.cn Subject: Re: [PATCH] mm/hugetlb: fix kernel NULL pointer dereference when replacing free hugetlb folios Message-ID: References: <1747884137-26685-1-git-send-email-yangge1116@126.com> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1747884137-26685-1-git-send-email-yangge1116@126.com> X-Spamd-Result: default: False [-4.51 / 50.00]; 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RCPT_COUNT_SEVEN(0.00)[10]; MISSING_XM_UA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:rdns,imap1.dmz-prg2.suse.org:helo,localhost.localdomain:mid] X-Rspamd-Action: no action X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Spam-Score: -4.51 X-Rspamd-Queue-Id: 4B41221747 X-Spam-Level: X-Spam-Flag: NO On Thu, May 22, 2025 at 11:22:17AM +0800, yangge1116@126.com wrote: > From: Ge Yang > > A kernel crash was observed when replacing free hugetlb folios: > > BUG: kernel NULL pointer dereference, address: 0000000000000028 > PGD 0 P4D 0 > Oops: Oops: 0000 [#1] SMP NOPTI > CPU: 28 UID: 0 PID: 29639 Comm: test_cma.sh Tainted 6.15.0-rc6-zp #41 PREEMPT(voluntary) > RIP: 0010:alloc_and_dissolve_hugetlb_folio+0x1d/0x1f0 > RSP: 0018:ffffc9000b30fa90 EFLAGS: 00010286 > RAX: 0000000000000000 RBX: 0000000000342cca RCX: ffffea0043000000 > RDX: ffffc9000b30fb08 RSI: ffffea0043000000 RDI: 0000000000000000 > RBP: ffffc9000b30fb20 R08: 0000000000001000 R09: 0000000000000000 > R10: ffff88886f92eb00 R11: 0000000000000000 R12: ffffea0043000000 > R13: 0000000000000000 R14: 00000000010c0200 R15: 0000000000000004 > FS: 00007fcda5f14740(0000) GS:ffff8888ec1d8000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 0000000000000028 CR3: 0000000391402000 CR4: 0000000000350ef0 > Call Trace: > > replace_free_hugepage_folios+0xb6/0x100 > alloc_contig_range_noprof+0x18a/0x590 > ? srso_return_thunk+0x5/0x5f > ? down_read+0x12/0xa0 > ? srso_return_thunk+0x5/0x5f > cma_range_alloc.constprop.0+0x131/0x290 > __cma_alloc+0xcf/0x2c0 > cma_alloc_write+0x43/0xb0 > simple_attr_write_xsigned.constprop.0.isra.0+0xb2/0x110 > debugfs_attr_write+0x46/0x70 > full_proxy_write+0x62/0xa0 > vfs_write+0xf8/0x420 > ? srso_return_thunk+0x5/0x5f > ? filp_flush+0x86/0xa0 > ? srso_return_thunk+0x5/0x5f > ? filp_close+0x1f/0x30 > ? srso_return_thunk+0x5/0x5f > ? do_dup2+0xaf/0x160 > ? srso_return_thunk+0x5/0x5f > ksys_write+0x65/0xe0 > do_syscall_64+0x64/0x170 > entry_SYSCALL_64_after_hwframe+0x76/0x7e > > There is a potential race between __update_and_free_hugetlb_folio() > and replace_free_hugepage_folios(): > > CPU1 CPU2 > __update_and_free_hugetlb_folio replace_free_hugepage_folios > folio_test_hugetlb(folio) > -- It's still hugetlb folio. > > __folio_clear_hugetlb(folio) > hugetlb_free_folio(folio) > h = folio_hstate(folio) > -- Here, h is NULL pointer > > When the above race condition occurs, folio_hstate(folio) returns > NULL, and subsequent access to this NULL pointer will cause the > system to crash. To resolve this issue, execute folio_hstate(folio) > under the protection of the hugetlb_lock lock, ensuring that > folio_hstate(folio) does not return NULL. > > Fixes: 04f13d241b8b ("mm: replace free hugepage folios after migration") > Signed-off-by: Ge Yang > Cc: Reviewed-by: Oscar Salvador -- Oscar Salvador SUSE Labs