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Tue, 21 May 2024 07:35:03 +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 totQM6dOTGZSfQAAD6G6ig (envelope-from ); Tue, 21 May 2024 07:35:03 +0000 From: Oscar Salvador To: Andrew Morton Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Muchun Song , Vishal Moola , Oscar Salvador Subject: [PATCH] mm/hugetlb: Move vmf_anon_prepare upfront in hugetlb_wp Date: Tue, 21 May 2024 09:34:46 +0200 Message-ID: <20240521073446.23185-1-osalvador@suse.de> X-Mailer: git-send-email 2.44.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Spam-Flag: NO X-Spam-Score: -1.30 X-Spam-Level: X-Spamd-Result: default: False [-1.30 / 50.00]; BAYES_HAM(-3.00)[100.00%]; SUSPICIOUS_RECIPS(1.50)[]; MID_CONTAINS_FROM(1.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_MISSING_CHARSET(0.50)[]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo,suse.de:email]; RCVD_VIA_SMTP_AUTH(0.00)[]; TAGGED_RCPT(0.00)[]; ARC_NA(0.00)[]; TO_DN_SOME(0.00)[]; MIME_TRACE(0.00)[0:+]; FREEMAIL_CC(0.00)[vger.kernel.org,kvack.org,linux.dev,gmail.com,suse.de]; RCVD_TLS_ALL(0.00)[]; FROM_HAS_DN(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; FUZZY_BLOCKED(0.00)[rspamd.com]; RCPT_COUNT_FIVE(0.00)[6]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FREEMAIL_ENVRCPT(0.00)[gmail.com] Content-Type: text/plain; charset="utf-8" hugetlb_wp calls vmf_anon_prepare() after having allocated a page, which means that we might need to call restore_reserve_on_error() upon error. vmf_anon_prepare() releases the vma lock before returning, but restore_reserve_on_error() expects the vma lock to be held by the caller. Fix it by calling vmf_anon_prepare() before allocating the page. Signed-off-by: Oscar Salvador Fixes: 9acad7ba3e25 ("hugetlb: use vmf_anon_prepare() instead of anon_vma_p= repare()") --- I did not hit this bug, I just spotted this because I was looking at hugetl= b_wp for some other reason. And I did not want to get creative to see if I could trigger this so I could get a backtrace. My assumption is that we could trigger this if 1) this was a shared mapping, so no anon_vma and 2) we call in GUP code with FOLL_WRITE, which would cause the FLAG_UNSHARE to be passed, so we will end up in hugetlb_wp(). mm/hugetlb.c | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 6be78e7d4f6e..eb0d8a45505e 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -6005,6 +6005,15 @@ static vm_fault_t hugetlb_wp(struct folio *pagecache= _folio, * be acquired again before returning to the caller, as expected. */ spin_unlock(vmf->ptl); + + /* + * When the original hugepage is shared one, it does not have + * anon_vma prepared. + */ + ret =3D vmf_anon_prepare(vmf); + if (unlikely(ret)) + goto out_release_old; + new_folio =3D alloc_hugetlb_folio(vma, vmf->address, outside_reserve); =20 if (IS_ERR(new_folio)) { @@ -6058,14 +6067,6 @@ static vm_fault_t hugetlb_wp(struct folio *pagecache= _folio, goto out_release_old; } =20 - /* - * When the original hugepage is shared one, it does not have - * anon_vma prepared. - */ - ret =3D vmf_anon_prepare(vmf); - if (unlikely(ret)) - goto out_release_all; - if (copy_user_large_folio(new_folio, old_folio, vmf->real_address, vma)) { ret =3D VM_FAULT_HWPOISON_LARGE | VM_FAULT_SET_HINDEX(hstate_index(h)); goto out_release_all; --=20 2.45.1