1From a02091834d3e167320d8a262ff04b8e83c5e616d Mon Sep 17 00:00:00 2001 2From: Darren Kenny <darren.kenny@oracle.com> 3Date: Tue, 24 Nov 2020 16:41:49 +0000 4Subject: [PATCH] zfs: Fix possible negative shift operation 5 6While it is possible for the return value from zfs_log2() to be zero 7(0), it is quite unlikely, given that the previous assignment to blksz 8is shifted up by SPA_MINBLOCKSHIFT (9) before 9 is subtracted at the 9assignment to epbs. 10 11But, while unlikely during a normal operation, it may be that a carefully 12crafted ZFS filesystem could result in a zero (0) value to the 13dn_datalbkszsec field, which means that the shift left does nothing 14and assigns zero (0) to blksz, resulting in a negative epbs value. 15 16Fixes: CID 73608 17 18Signed-off-by: Darren Kenny <darren.kenny@oracle.com> 19Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com> 20Signed-off-by: Stefan Sørensen <stefan.sorensen@spectralink.com> 21--- 22 grub-core/fs/zfs/zfs.c | 5 +++++ 23 1 file changed, 5 insertions(+) 24 25diff --git a/grub-core/fs/zfs/zfs.c b/grub-core/fs/zfs/zfs.c 26index 36d0373..0c42cba 100644 27--- a/grub-core/fs/zfs/zfs.c 28+++ b/grub-core/fs/zfs/zfs.c 29@@ -2667,6 +2667,11 @@ dnode_get (dnode_end_t * mdn, grub_uint64_t objnum, grub_uint8_t type, 30 blksz = grub_zfs_to_cpu16 (mdn->dn.dn_datablkszsec, 31 mdn->endian) << SPA_MINBLOCKSHIFT; 32 epbs = zfs_log2 (blksz) - DNODE_SHIFT; 33+ 34+ /* While this should never happen, we should check that epbs is not negative. */ 35+ if (epbs < 0) 36+ epbs = 0; 37+ 38 blkid = objnum >> epbs; 39 idx = objnum & ((1 << epbs) - 1); 40 41-- 422.14.2 43 44