Testing of a new feature revealed that calling sysctl() to retrieve
the value of the user.localbase variable passing too low a buffer size
could leave the result buffer unchanged.
The behavior in the normal case of a sufficiently large buffer was
correct.
All known callers pass a sufficiently large buffer and have thus not
been affected by this issue. If a non-default value had been assigned
to this variable, the result was as documented, too.
Fix the function to fill the buffer with a partial result, if the
passed in buffer size is too low to hold the full result.
(cherry picked from commit e11ad014d1)
libc: add helper furnction to set sysctl() user.* variables
Testing had revealed that trying to retrieve the user.localbase
variable into to small a buffer would return the correct error code,
but would not fill the available buffer space with a partial result.
A partial result is of no use, but this is still a violation of the
documented behavior, which has been fixed in the previous commit to
this function.
I just checked the code for "user.cs_path" and found that it had the
same issue.
Instead of fixing the logic for each user.* sysctl string variable
individually, this commit adds a helper function set_user_str() that
implements the semantics specified in the sysctl() man page.
It is currently only used for "user.cs_path" and "user.localbase",
but it will offer a significant simplification when further such
variables will be added (as I intend to do).
(cherry picked from commit 9535d9f104)
sysctlbyname(): restore access to user variables
The optimization of sysctlbyname() in commit d05b53e0ba had the
side-effect of not going through the fix-up for the user.* variables
in the previously called sysctl() function.
This lead to 0 or an empty strings being returned by sysctlbyname()
for all user.* variables.
An alternate implementation would store the user variables in the
kernel during system start-up. That would allow to remove the fix-up
code in the C library that is currently required to provide the actual
values.
This update restores the previous code path for the user.* variables
and keeps the performance optimization intact for all other variables.
(cherry picked from commit af7d105379)
23fe1083ca