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Howlett" Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Jann Horn , Suren Baghdasaryan , Matthew Wilcox , stable@vger.kernel.org References: <20230929183041.2835469-1-Liam.Howlett@oracle.com> <20230929183041.2835469-3-Liam.Howlett@oracle.com> <843f059f-dd54-4481-b46a-e87e56274db3@lucifer.local> From: Vlastimil Babka In-Reply-To: <843f059f-dd54-4481-b46a-e87e56274db3@lucifer.local> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 8ABA7A0020 X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: tynzmoup343yfg6s7xbgw58bogrxa1t6 X-HE-Tag: 1696231565-530552 X-HE-Meta: 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 5LYaFOmC shE5yRnBAOvvsafBb/p9K3wQmMYp5cLQHP0hHpxOYo1wSJsvES4Nid1Ian+2g4Q05tQcwO+EEfbHXSwkrHXRLoyPNaNvoBhBlk91BvZ0WHwp8RLqp3NWkq+VBtlDWqyh2oMrWIvftRjolBbVv93VCd3/oF/M4SkivATWWjNTOWzO9rOman9UNDgz2ad6IgHjkrxSMrJci6wdtY3QAYXOAiI+EJhI5U3RysJtGIHyghwWgPLfyMMGT+FDcVdEgPhEhCPXzDUtin8SwVWRVSN1MMHlbYp1SLTX7eF4RZgqMNIkMNvRl5ej/g1Hs4kqVjzruX3NpdpOeKNHbXwM1NgHV5/3E6+wAzUXXw0SA X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 9/30/23 00:28, Lorenzo Stoakes wrote: > On Fri, Sep 29, 2023 at 02:30:40PM -0400, Liam R. Howlett wrote: >> When the calling function fails after the dup_anon_vma(), the >> duplication of the anon_vma is not being undone. Add the necessary >> unlink_anon_vma() call to the error paths that are missing them. >> >> This issue showed up during inspection of the error path in vma_merge() >> for an unrelated vma iterator issue. >> >> Users may experience increased memory usage, which may be problematic as >> the failure would likely be caused by a low memory situation. >> >> Fixes: d4af56c5c7c6 ("mm: start tracking VMAs with maple tree") >> Cc: stable@vger.kernel.org >> Cc: Jann Horn >> Signed-off-by: Liam R. Howlett >> --- >> mm/mmap.c | 30 ++++++++++++++++++++++-------- >> 1 file changed, 22 insertions(+), 8 deletions(-) >> >> diff --git a/mm/mmap.c b/mm/mmap.c >> index acb7dea49e23..f9f0a5fe4db4 100644 >> --- a/mm/mmap.c >> +++ b/mm/mmap.c >> @@ -583,11 +583,12 @@ static inline void vma_complete(struct vma_prepare *vp, >> * dup_anon_vma() - Helper function to duplicate anon_vma >> * @dst: The destination VMA >> * @src: The source VMA >> + * @dup: Pointer to the destination VMA when successful. >> * >> * Returns: 0 on success. > > Being a bit nitpicky/refactory here, but anon_vma_clone() appears to have > two possible return values - 0 for success, and -ENOMEM. > > As a result, it's not really gaining us much passing through this value. > > It'd be nice if dup_anon_vma() and anon_vma_clone() were therefore updated > to instead return NULL on ENOMEM and the dst otherwise. But we also need to represent that dup_anon_vma() had nothing to do, because "(src->anon_vma && !dst->anon_vma)" was false, and in that case we should not be returning dst from there? So maybe we could return NULL for that case and ERR_PTR(ret) for the -ENOMEM from anon_vma_clone() ? > Then we could de-clunk this whole code path, and the quite natural fact of > 'thing didn't return a pointer therefore had no memory to allocate it' fals > out. > > But this isn't exactly an earth-shattering concern :) >