[4.9,102/128] ext4: fix EXT_MAX_EXTENT/INDEX to check for zeroed eh_max

Message ID 20200619141625.517958714@linuxfoundation.org
State Superseded
Headers show
Series
  • Untitled series #28329
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Commit Message

Greg Kroah-Hartman June 19, 2020, 2:33 p.m.
From: Harshad Shirwadkar <harshadshirwadkar@gmail.com>

commit c36a71b4e35ab35340facdd6964a00956b9fef0a upstream.

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 <harshadshirwadkar@gmail.com>
Link: https://lore.kernel.org/r/20200421023959.20879-2-harshadshirwadkar@gmail.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/ext4/ext4_extents.h |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

Patch

--- a/fs/ext4/ext4_extents.h
+++ b/fs/ext4/ext4_extents.h
@@ -169,10 +169,13 @@  struct ext4_ext_path {
 	(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)
 {