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charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.60.1 (by Flathub.org) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Mon, 2026-08-10 at 17:24 +0800, Jiaming Zhang wrote: > __hfsplus_ext_write_extent() writes the cached extent record back > into a > B-tree node using fd->entrylength as the length, and fd->entrylength > is > derived in __hfs_brec_find() from two on-disk values: >=20 > fd->entrylength =3D len - keylen; >=20 > A crafted image can keep both len and keylen valid but make fd- > >entrylength > negative (keylen > len). __hfsplus_ext_write_extent() doesn't check > fd->entrylength before consuming it, and hfs_bnode_write() takes the > length > as u32, so the negative value turns into a huge one. The copy then > reads > data past the end of hip->cached_extents, which is only > sizeof(hfsplus_extent_rec) bytes long, and leaks kernel memory into > the > image. >=20 > Reject an fd->entrylength that does not match > sizeof(hfsplus_extent_rec) in > __hfsplus_ext_write_extent(), mirroring the check already performed > in > __hfsplus_ext_read_extent(). >=20 > Link: > https://lore.kernel.org/lkml/cbd7003314c530d4f910eacf019ff80adad6687e.cam= el@dubeyko.com/ > Signed-off-by: Jiaming Zhang > --- > =C2=A0fs/hfsplus/extents.c | 2 ++ > =C2=A01 file changed, 2 insertions(+) >=20 > diff --git a/fs/hfsplus/extents.c b/fs/hfsplus/extents.c > index 813e68b8ecd6..eb7c11524d18 100644 > --- a/fs/hfsplus/extents.c > +++ b/fs/hfsplus/extents.c > @@ -110,6 +110,8 @@ static int __hfsplus_ext_write_extent(struct > inode *inode, > =C2=A0 } else { > =C2=A0 if (res) > =C2=A0 return res; > + if (fd->entrylength !=3D sizeof(hfsplus_extent_rec)) > + return -EIO; > =C2=A0 hfs_bnode_write(fd->bnode, hip->cached_extents, > =C2=A0 fd->entryoffset, fd->entrylength); > =C2=A0 hip->extent_state &=3D ~HFSPLUS_EXT_DIRTY; Looks good. Reviewed-by: Viacheslav Dubeyko Thanks, Slava.