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s390/ipl: Do not accept z/VM CP diag X'008' cmds longer than max length

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The old implementation of vmcmd sysfs string attributes truncated passed
z/VM CP diagnose X'008' commands which were longer than the max allowed
number of characters but the reported number of written characters was
still equal to the entire length of a given string. This can result in
silent failures of some s390-tools (e.g. dumpconf) which can be very hard
to detect. Therefore, this commit makes a write attempt to a vmcmd sysfs
attribute
* fail with E2BIG error if a given string is longer than the maximum
  allowed one
* never destroy the old data in the vmcmd sysfs attribute if the new data
  doesn't fit into it entirely
* return the actual number of written characters if it succeeds

Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Egorenkov <egorenar@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
This commit is contained in:
Alexander Egorenkov 2024-05-10 11:39:53 +02:00 committed by Alexander Gordeev
parent 72935e3ada
commit 247576bf62
1 changed files with 5 additions and 1 deletions
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6
arch/s390/kernel/ipl.c
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@ -266,7 +266,11 @@ static ssize_t sys_##_prefix##_##_name##_store(struct kobject *kobj, \
struct kobj_attribute *attr, \
const char *buf, size_t len) \
{ \
strscpy(_value, buf, sizeof(_value)); \
if (len >= sizeof(_value)) \
return -E2BIG; \
len = strscpy(_value, buf, sizeof(_value)); \
if (len < 0) \
return len; \
strim(_value); \
return len; \
} \