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V" , Nicholas Piggin , "Kirill A . Shutemov" , Alexei Starovoitov , Andy Lutomirski , Donet Tom Subject: [PATCH] fs/hugetlbfs/inode.c: Ensure generic_hugetlb_get_unmapped_area() returns higher address than mmap_min_addr Date: Fri, 5 Jul 2024 02:11:50 -0500 Message-ID: <20240705071150.84972-1-donettom@linux.ibm.com> X-Mailer: git-send-email 2.43.5 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-TM-AS-GCONF: 00 X-Proofpoint-GUID: 7xL22XUaxd0RtczpMHp9W9I0o08bZ7zO X-Proofpoint-ORIG-GUID: dwdz3dUsdfw1_XqqRJX1qMvD6o-kHuMl 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=2024-07-05_03,2024-07-03_01,2024-05-17_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 bulkscore=0 spamscore=0 phishscore=0 malwarescore=0 lowpriorityscore=0 priorityscore=1501 mlxscore=0 suspectscore=0 impostorscore=0 mlxlogscore=921 clxscore=1011 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2406140001 definitions=main-2407050049 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. 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! # Reported-by Pavithra Prakash Signed-off-by: Donet Tom Reported-by Pavithra Prakash --- fs/hugetlbfs/inode.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c index 412f295acebe..428fd2f0e4c4 100644 --- a/fs/hugetlbfs/inode.c +++ b/fs/hugetlbfs/inode.c @@ -228,7 +228,7 @@ generic_hugetlb_get_unmapped_area(struct file *file, un= signed long addr, =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) { @@ -240,7 +240,7 @@ generic_hugetlb_get_unmapped_area(struct file *file, un= signed long addr, if (addr) { addr =3D ALIGN(addr, huge_page_size(h)); vma =3D find_vma(mm, addr); - if (mmap_end - len >=3D addr && + if (mmap_end - len >=3D addr && addr >=3D mmap_min_addr && (!vma || addr + len <=3D vm_start_gap(vma))) return addr; } --=20 2.43.5