On Tue, Jul 30, 2024 at 07:23:04PM +0200, Thorsten Blum wrote: > Add the __counted_by compiler attribute to the flexible array member > inodes to improve access bounds-checking via CONFIG_UBSAN_BOUNDS and > CONFIG_FORTIFY_SOURCE. > > Remove the now obsolete comment on the count field. > > Refactor ext4_expand_inode_array() by assigning count before copying any > data using memcpy(). Copy only the inodes array instead of the whole > struct because count has been set explicitly. > > Use struct_size() and struct_size_t() instead of offsetof(). > > Change the data type of the local variable count to unsigned int to > match the struct's count data type. > > Compile-tested only. > > Signed-off-by: Thorsten Blum <thorsten.blum@xxxxxxxxxx> > --- > Changes in v2: > - Adjust ext4_expand_inode_array() as suggested by Gustavo A. R. Silva > - Use struct_size() and struct_size_t() instead of offsetof() > - Link to v1: https://lore.kernel.org/linux-kernel/20240729110454.346918-3-thorsten.blum@xxxxxxxxxx/ > --- > fs/ext4/xattr.c | 20 +++++++++----------- > fs/ext4/xattr.h | 4 ++-- > 2 files changed, 11 insertions(+), 13 deletions(-) > > diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c > index 46ce2f21fef9..b27543587103 100644 > --- a/fs/ext4/xattr.c > +++ b/fs/ext4/xattr.c > @@ -2879,11 +2879,10 @@ ext4_expand_inode_array(struct ext4_xattr_inode_array **ea_inode_array, > if (*ea_inode_array == NULL) { > /* > * Start with 15 inodes, so it fits into a power-of-two size. > - * If *ea_inode_array is NULL, this is essentially offsetof() > */ > (*ea_inode_array) = > - kmalloc(offsetof(struct ext4_xattr_inode_array, > - inodes[EIA_MASK]), > + kmalloc(struct_size_t(struct ext4_xattr_inode_array, This can be struct_size(*ea_inode_array, ...) too, like you have below. > + inodes, EIA_MASK), > GFP_NOFS); > if (*ea_inode_array == NULL) > return -ENOMEM; > @@ -2891,17 +2890,16 @@ ext4_expand_inode_array(struct ext4_xattr_inode_array **ea_inode_array, > } else if (((*ea_inode_array)->count & EIA_MASK) == EIA_MASK) { > /* expand the array once all 15 + n * 16 slots are full */ > struct ext4_xattr_inode_array *new_array = NULL; > - int count = (*ea_inode_array)->count; > + unsigned int count = (*ea_inode_array)->count; > > - /* if new_array is NULL, this is essentially offsetof() */ > - new_array = kmalloc( > - offsetof(struct ext4_xattr_inode_array, > - inodes[count + EIA_INCR]), > - GFP_NOFS); > + new_array = kmalloc(struct_size(*ea_inode_array, inodes, > + count + EIA_INCR), > + GFP_NOFS); > if (new_array == NULL) > return -ENOMEM; > - memcpy(new_array, *ea_inode_array, > - offsetof(struct ext4_xattr_inode_array, inodes[count])); > + new_array->count = count; > + memcpy(new_array->inodes, (*ea_inode_array)->inodes, > + count * sizeof(struct inode *)); > kfree(*ea_inode_array); > *ea_inode_array = new_array; > } > diff --git a/fs/ext4/xattr.h b/fs/ext4/xattr.h > index bd97c4aa8177..e14fb19dc912 100644 > --- a/fs/ext4/xattr.h > +++ b/fs/ext4/xattr.h > @@ -130,8 +130,8 @@ struct ext4_xattr_ibody_find { > }; > > struct ext4_xattr_inode_array { > - unsigned int count; /* # of used items in the array */ > - struct inode *inodes[]; > + unsigned int count; > + struct inode *inodes[] __counted_by(count); > }; > > extern const struct xattr_handler ext4_xattr_user_handler; Thanks for the reworking! -- Kees Cook
