diff options
| author | Paul Burton <paul.burton@imgtec.com> | 2016-08-19 17:43:56 +0100 |
|---|---|---|
| committer | Martin K. Petersen <martin.petersen@oracle.com> | 2016-08-30 22:18:10 -0400 |
| commit | b9b6e80ad3b11778f1066d698a838bcc86efb6be (patch) | |
| tree | 0039f99a52217a0446dd079ba90edab4fe1c5328 /drivers | |
| parent | a6104b1e1846273d52b9230d700939fef0a9da80 (diff) | |
scsi: sg: Avoid overflow when USER_HZ > HZ
Calculating the maximum timeout that a user can set via the
SG_SET_TIMEOUT ioctl involves multiplying INT_MAX by USER_HZ/HZ. If
USER_HZ is larger than HZ then this results in an overflow when
performed as a 32 bit integer calculation, resulting in compiler
warnings such as the following:
drivers/scsi/sg.c: In function 'sg_ioctl':
drivers/scsi/sg.c:91:67: warning: integer overflow in expression [-Woverflow]
#define MULDIV(X,MUL,DIV) ((((X % DIV) * MUL) / DIV) + ((X / DIV) * MUL))
^
drivers/scsi/sg.c:887:14: note: in expansion of macro 'MULDIV'
if (val >= MULDIV (INT_MAX, USER_HZ, HZ))
^
drivers/scsi/sg.c:91:67: warning: integer overflow in expression [-Woverflow]
#define MULDIV(X,MUL,DIV) ((((X % DIV) * MUL) / DIV) + ((X / DIV) * MUL))
^
drivers/scsi/sg.c:888:13: note: in expansion of macro 'MULDIV'
val = MULDIV (INT_MAX, USER_HZ, HZ);
^
Avoid this overflow by performing the (constant) arithmetic on 64 bit
integers, which ensures that overflow from multiplying the 32 bit values
cannot occur. When converting the result back to a 32 bit integer use
min_t to ensure that we don't simply truncate a value beyond INT_MAX to
a 32 bit integer, but instead use INT_MAX where the result was larger
than it. As the values are all compile time constant the 64 bit
arithmetic should have no runtime cost.
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Acked-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/scsi/sg.c | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c index ae7d9bdf409c..bb5ec2d6abdf 100644 --- a/drivers/scsi/sg.c +++ b/drivers/scsi/sg.c @@ -884,8 +884,9 @@ sg_ioctl(struct file *filp, unsigned int cmd_in, unsigned long arg) return result; if (val < 0) return -EIO; - if (val >= MULDIV (INT_MAX, USER_HZ, HZ)) - val = MULDIV (INT_MAX, USER_HZ, HZ); + if (val >= MULDIV((s64)INT_MAX, USER_HZ, HZ)) + val = min_t(s64, MULDIV((s64)INT_MAX, USER_HZ, HZ), + INT_MAX); sfp->timeout_user = val; sfp->timeout = MULDIV (val, HZ, USER_HZ); |