From c36a71b4e35ab35340facdd6964a00956b9fef0a Mon Sep 17 00:00:00 2001 From: Harshad Shirwadkar Date: Mon, 20 Apr 2020 19:39:59 -0700 Subject: [PATCH] ext4: fix EXT_MAX_EXTENT/INDEX to check for zeroed eh_max If eh->eh_max is 0, EXT_MAX_EXTENT/INDEX would evaluate to unsigned (-1) resulting in illegal memory accesses. Although there is no consistent repro, we see that generic/019 sometimes crashes because of this bug. Ran gce-xfstests smoke and verified that there were no regressions. Signed-off-by: Harshad Shirwadkar Link: https://lore.kernel.org/r/20200421023959.20879-2-harshadshirwadkar@gmail.com Signed-off-by: Theodore Ts'o Cc: stable@kernel.org --- fs/ext4/ext4_extents.h | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/fs/ext4/ext4_extents.h b/fs/ext4/ext4_extents.h index 1c216fc..44e5988 100644 --- a/fs/ext4/ext4_extents.h +++ b/fs/ext4/ext4_extents.h @@ -170,10 +170,13 @@ struct partial_cluster { (EXT_FIRST_EXTENT((__hdr__)) + le16_to_cpu((__hdr__)->eh_entries) - 1) #define EXT_LAST_INDEX(__hdr__) \ (EXT_FIRST_INDEX((__hdr__)) + le16_to_cpu((__hdr__)->eh_entries) - 1) -#define EXT_MAX_EXTENT(__hdr__) \ - (EXT_FIRST_EXTENT((__hdr__)) + le16_to_cpu((__hdr__)->eh_max) - 1) +#define EXT_MAX_EXTENT(__hdr__) \ + ((le16_to_cpu((__hdr__)->eh_max)) ? \ + ((EXT_FIRST_EXTENT((__hdr__)) + le16_to_cpu((__hdr__)->eh_max) - 1)) \ + : 0) #define EXT_MAX_INDEX(__hdr__) \ - (EXT_FIRST_INDEX((__hdr__)) + le16_to_cpu((__hdr__)->eh_max) - 1) + ((le16_to_cpu((__hdr__)->eh_max)) ? \ + ((EXT_FIRST_INDEX((__hdr__)) + le16_to_cpu((__hdr__)->eh_max) - 1)) : 0) static inline struct ext4_extent_header *ext_inode_hdr(struct inode *inode) { -- 2.7.4