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jfs: avoid undefined behavior from left-shifting by 32 bits

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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>
This commit is contained in:
Nickolai Zeldovich 2013-01-05 14:19:21 -05:00 committed by Dave Kleikamp
parent 5f243b9b46
commit 9d48017bce
1 changed files with 1 additions and 1 deletions
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fs/jfs/jfs_imap.c
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@ -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;