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charset="UTF-8" X-Stat-Signature: yjk95p5s6tcrqdjzeiu3zekiszj7g4dg X-Rspam-User: X-Spamd-Result: default: False [-1.80 / 9.00]; BAYES_HAM(-5.90)[99.78%]; SORBS_IRL_BL(3.00)[209.85.166.176:from]; SUBJECT_HAS_UNDERSCORES(1.00)[]; RCVD_NO_TLS_LAST(0.10)[]; MIME_GOOD(-0.10)[text/plain]; BAD_REP_POLICIES(0.10)[]; R_SPF_ALLOW(0.00)[+ip4:209.85.128.0/17]; R_DKIM_ALLOW(0.00)[google.com:s=20210112]; RCPT_COUNT_SEVEN(0.00)[9]; FROM_EQ_ENVFROM(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; MIME_TRACE(0.00)[0:+]; TO_DN_SOME(0.00)[]; DMARC_POLICY_ALLOW(0.00)[google.com,reject]; TO_MATCH_ENVRCPT_SOME(0.00)[]; FROM_HAS_DN(0.00)[]; DKIM_TRACE(0.00)[google.com:+]; PREVIOUSLY_DELIVERED(0.00)[linux-mm@kvack.org]; ARC_NA(0.00)[]; ARC_SIGNED(0.00)[hostedemail.com:s=arc-20220608:i=1]; TO_DN_EQ_ADDR_SOME(0.00)[] X-Rspamd-Queue-Id: 33C73180017 X-Rspamd-Server: rspam06 X-HE-Tag: 1670260583-540538 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 Mon, Dec 5, 2022 at 5:53 PM Liam Howlett wrote: > Add more sanity checks to the VMA that do_brk_flags() will expand. > Ensure the VMA matches basic merge requirements within the function > before calling can_vma_merge_after(). > > Drop the duplicate checks from vm_brk_flags() since they will be > enforced later. Looks good to me, with one note: > Fixes: 2e7ce7d354f2 ("mm/mmap: change do_brk_flags() to expand existing VMA and add do_brk_munmap()") > Suggested-by: Jann Horn > Signed-off-by: Liam R. Howlett > --- > mm/mmap.c | 11 +++-------- > 1 file changed, 3 insertions(+), 8 deletions(-) > > diff --git a/mm/mmap.c b/mm/mmap.c > index a5eb2f175da0..41a2c42593e8 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -2946,9 +2946,9 @@ static int do_brk_flags(struct ma_state *mas, struct vm_area_struct *vma, > * Expand the existing vma if possible; Note that singular lists do not > * occur after forking, so the expand will only happen on new VMAs. > */ > - if (vma && > - (!vma->anon_vma || list_is_singular(&vma->anon_vma_chain)) && > - ((vma->vm_flags & ~VM_SOFTDIRTY) == flags)) { > + if (vma && vma->vm_end == addr && !vma_policy(vma) && vma->anon_vma && Why the "vma->anon_vma" check here? The old code was checking that the existing VMA is not attached to more than one anon_vma; but the new code instead checks that the existing VMA is attached to at least one anon_vma, and then is_mergeable_anon_vma() checks that the VMA is not attached to more than one anon_vma, so in effect the VMA has to be attached to exactly one anon_vma. Is that intentional? If not, maybe delete the "vma->anon_vma &&" - can_vma_merge_after() already does the equivalent check of the old "(!vma->anon_vma || list_is_singular(&vma->anon_vma_chain))". > + can_vma_merge_after(vma, flags, NULL, NULL, > + addr >> PAGE_SHIFT, NULL_VM_UFFD_CTX, NULL)) { > mas_set_range(mas, vma->vm_start, addr + len - 1); > if (mas_preallocate(mas, vma, GFP_KERNEL)) > return -ENOMEM; > @@ -3035,11 +3035,6 @@ int vm_brk_flags(unsigned long addr, unsigned long request, unsigned long flags) > goto munmap_failed; > > vma = mas_prev(&mas, 0); > - if (!vma || vma->vm_end != addr || vma_policy(vma) || > - !can_vma_merge_after(vma, flags, NULL, NULL, > - addr >> PAGE_SHIFT, NULL_VM_UFFD_CTX, NULL)) > - vma = NULL; > - > ret = do_brk_flags(&mas, vma, addr, len, flags); > populate = ((mm->def_flags & VM_LOCKED) != 0); > mmap_write_unlock(mm); > -- > 2.35.1