Is the pointer guaranteed to be aligned? If not you have to use unaligned access. Any reason not to check it against correct magic and not just zero-out?
Le dim. 11 févr. 2024, 18:36, Jon DeVree <n...@vault24.org> a écrit : > The directory extent list does not have to be a continuous list of data > blocks. When GRUB tries to read a non-existant member of the list, > grub_xfs_read_file() will return a block of zero'ed memory. Checking for > a zero'ed magic number is sufficient to skip this non-existant data > block. > > Prior to commit 07318ee7e this was handled as a subtle side effect of > reading the (non-existant) tail data structure. Since the block was > zero'ed the computation of the number of directory entries in the block > would return 0 as well. > > Fixes: 07318ee7e (fs/xfs: Fix XFS directory extent parsing) > Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=2254370 > Signed-off-by: Jon DeVree <n...@vault24.org> > --- > grub-core/fs/xfs.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/grub-core/fs/xfs.c b/grub-core/fs/xfs.c > index bc2224dbb..a6cce9cfe 100644 > --- a/grub-core/fs/xfs.c > +++ b/grub-core/fs/xfs.c > @@ -902,6 +902,7 @@ grub_xfs_iterate_dir (grub_fshelp_node_t dir, > grub_xfs_first_de(dir->data, > dirblock); > int entries = -1; > char *end = dirblock + dirblk_size; > + grub_uint32_t magic; > > numread = grub_xfs_read_file (dir, 0, 0, > blk << dirblk_log2, > @@ -912,6 +913,15 @@ grub_xfs_iterate_dir (grub_fshelp_node_t dir, > return 0; > } > > + /* > + * If this data block isn't actually part of the extent list > then > + * grub_xfs_read_file() returns a block of zeros. So if the > magic number > + * field is all zeros then this block should be skipped. > + */ > + magic = *(grub_uint32_t *)dirblock; > + if (!magic) > + continue; > + > /* > * Leaf and tail information are only in the data block if the > number > * of extents is 1. > -- > 2.43.0 > > > _______________________________________________ > Grub-devel mailing list > Grub-devel@gnu.org > https://lists.gnu.org/mailman/listinfo/grub-devel >
_______________________________________________ Grub-devel mailing list Grub-devel@gnu.org https://lists.gnu.org/mailman/listinfo/grub-devel
