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authorPaul Burton <paul.burton@imgtec.com>2016-08-19 17:43:56 +0100
committerMartin K. Petersen <martin.petersen@oracle.com>2016-08-30 22:18:10 -0400
commitb9b6e80ad3b11778f1066d698a838bcc86efb6be (patch)
tree0039f99a52217a0446dd079ba90edab4fe1c5328 /drivers/scsi/sg.c
parenta6104b1e1846273d52b9230d700939fef0a9da80 (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/scsi/sg.c')
-rw-r--r--drivers/scsi/sg.c5
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);

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