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Shutemov" Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Ritesh Harjani , Mike Rapoport , David Hildenbrand , Matthew Wilcox , Tony Battersby , "Aneesh Kumar K . V" , Nicholas Piggin , Alexei Starovoitov , Andy Lutomirski , Donet Tom Subject: [PATCH v3] hugetlbfs: Ensure generic_hugetlb_get_unmapped_area() returns higher address than mmap_min_addr Date: Wed, 10 Jul 2024 00:19:12 -0500 Message-ID: <20240710051912.4681-1-donettom@linux.ibm.com> X-Mailer: git-send-email 2.43.5 X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: eXjPB2DIEx78qqOf_HQlGo0-EbgYisCH X-Proofpoint-GUID: BeQV48yM1TyCSP-cQFPb40GhdOf-yhbT Content-Transfer-Encoding: quoted-printable X-Proofpoint-UnRewURL: 0 URL was un-rewritten Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1039,Hydra:6.0.680,FMLib:17.12.28.16 definitions=2024-07-10_01,2024-07-09_01,2024-05-17_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 bulkscore=0 mlxscore=0 spamscore=0 malwarescore=0 phishscore=0 adultscore=0 impostorscore=0 mlxlogscore=999 suspectscore=0 priorityscore=1501 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2406140001 definitions=main-2407100036 Content-Type: text/plain; charset="utf-8" generic_hugetlb_get_unmapped_area() was returning an address less than mmap_min_addr if the mmap argument addr, after alignment, was less than mmap_min_addr, causing mmap to fail. This is because current generic_hugetlb_get_unmapped_area() code does not take into account mmap_min_addr. This patch ensures that generic_hugetlb_get_unmapped_area() always returns an address that is greater than mmap_min_addr. Additionally, similar to generic_get_unmapped_area(), vm_end_gap() checks are included to maintain stack gap. How to reproduce =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D #include #include #include #include #define HUGEPAGE_SIZE (16 * 1024 * 1024) int main() { void *addr =3D mmap((void *)-1, HUGEPAGE_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS | MAP_HUGETLB, -1, 0); if (addr =3D=3D MAP_FAILED) { perror("mmap"); exit(EXIT_FAILURE); } snprintf((char *)addr, HUGEPAGE_SIZE, "Hello, Huge Pages!"); printf("%s\n", (char *)addr); if (munmap(addr, HUGEPAGE_SIZE) =3D=3D -1) { perror("munmap"); exit(EXIT_FAILURE); } return 0; } Result without fix =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D # cat /proc/meminfo |grep -i HugePages_Free HugePages_Free: 20 # ./test mmap: Permission denied # Result with fix =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D # cat /proc/meminfo |grep -i HugePages_Free HugePages_Free: 20 # ./test Hello, Huge Pages! # V3: Changed subject prefix and commit message. V2: Added vm_end_gap() check. https://lore.kernel.org/all/20240709092122.41232-1-donettom@linux.ibm.com/ V1: https://lore.kernel.org/all/20240705071150.84972-1-donettom@linux.ibm.com/ Reported-by Pavithra Prakash Signed-off-by: Donet Tom Acked-by: Kirill A. Shutemov Reported-by Pavithra Prakash --- fs/hugetlbfs/inode.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c index 412f295acebe..cdd8e53ddd19 100644 --- a/fs/hugetlbfs/inode.c +++ b/fs/hugetlbfs/inode.c @@ -222,13 +222,13 @@ generic_hugetlb_get_unmapped_area(struct file *file, = unsigned long addr, unsigned long flags) { struct mm_struct *mm =3D current->mm; - struct vm_area_struct *vma; + struct vm_area_struct *vma, *prev; struct hstate *h =3D hstate_file(file); const unsigned long mmap_end =3D arch_get_mmap_end(addr, len, flags); =20 if (len & ~huge_page_mask(h)) return -EINVAL; - if (len > TASK_SIZE) + if (len > mmap_end - mmap_min_addr) return -ENOMEM; =20 if (flags & MAP_FIXED) { @@ -239,9 +239,10 @@ generic_hugetlb_get_unmapped_area(struct file *file, u= nsigned long addr, =20 if (addr) { addr =3D ALIGN(addr, huge_page_size(h)); - vma =3D find_vma(mm, addr); - if (mmap_end - len >=3D addr && - (!vma || addr + len <=3D vm_start_gap(vma))) + vma =3D find_vma_prev(mm, addr, &prev); + if (mmap_end - len >=3D addr && addr >=3D mmap_min_addr && + (!vma || addr + len <=3D vm_start_gap(vma)) && + (!prev || addr >=3D vm_end_gap(prev))) return addr; } =20 --=20 2.43.5