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authorNickolai Zeldovich <nickolai@csail.mit.edu>2013-01-05 14:19:21 -0500
committerDave Kleikamp <dave.kleikamp@oracle.com>2013-01-07 08:21:36 -0600
commit9d48017bce890b19e3bba649850bdbc8a6f95903 (patch)
treeece6878230600e39daafc2169afaced628cac871 /fs/jfs/jfs_imap.c
parent5f243b9b46a22e5790dbbc36f574c2417af49a41 (diff)
jfs: avoid undefined behavior from left-shifting by 32 bits
Shifting a 32-bit int by 32 bits is undefined behavior in C, and results in different behavior on different architectures (e.g., x86 and PowerPC). diAlloc() in fs/jfs/jfs_imap.c computes a mask using 0xffffffffu<<(32-bitno), which can left-shift by 32 bits. To avoid unexpected behavior, explicitly check for bitno==0 and use a 0 mask. Signed-off-by: Nickolai Zeldovich <nickolai@csail.mit.edu> Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Diffstat (limited to 'fs/jfs/jfs_imap.c')
-rw-r--r--fs/jfs/jfs_imap.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/jfs/jfs_imap.c b/fs/jfs/jfs_imap.c
index 6ba4006e011b..f7e042b63ddb 100644
--- a/fs/jfs/jfs_imap.c
+++ b/fs/jfs/jfs_imap.c
@@ -1493,7 +1493,7 @@ int diAlloc(struct inode *pip, bool dir, struct inode *ip)
/* mask any prior bits for the starting words of the
* summary map.
*/
- mask = ONES << (EXTSPERSUM - bitno);
+ mask = (bitno == 0) ? 0 : (ONES << (EXTSPERSUM - bitno));
inosmap = le32_to_cpu(iagp->inosmap[sword]) | mask;
extsmap = le32_to_cpu(iagp->extsmap[sword]) | mask;