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Code Issues Releases Activity

Don't acquire sysctlmemlock in userland_sysctl() when the old value

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pointer is NULL, as in that case there are no userland pages that
could potentially be wired.  It is common for old to be NULL and
oldlenp to be non-NULL in calls to userland_sysctl(), as this is used
to probe for the length of a variable-length sysctl entry before
retrieving a value.  Note that it is typical for such calls to be made
with an uninitialized value in *oldlenp, so sysctlmemlock was
essentially being acquired at random (depending on the uninitialized
value in *oldlenp being > PAGE_SIZE or not) for these calls prior to
this patch.

Differential Revision: https://reviews.freebsd.org/D2987
Reviewed by: mjg, kib
Approved by: jmallett (mentor)
MFC after: 1 month
This commit is contained in:
Patrick Kelsey 2015-07-06 16:07:21 +00:00
parent 9889bbac23
commit 6f99ea0520
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=285208
1 changed files with 1 additions and 1 deletions
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2
sys/kern/kern_sysctl.c
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@ -1784,7 +1784,7 @@ userland_sysctl(struct thread *td, int *name, u_int namelen, void *old,
ktrsysctl(name, namelen);
#endif
if (req.oldlen > PAGE_SIZE) {
if (req.oldptr && req.oldlen > PAGE_SIZE) {
memlocked = 1;
sx_xlock(&sysctlmemlock);
} else