Messages in this thread Patch in this message | | | Date | Fri, 13 Mar 2020 09:43:06 -0700 | From | Eric Biggers <> | Subject | Re: [PATCH v3 3/3] KEYS: Use kvmalloc() to better handle large buffer allocation |
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On Fri, Mar 13, 2020 at 11:21:02AM -0400, Waiman Long wrote: > For large multi-page temporary buffer allocation, the security/keys > subsystem don't need contiguous physical pages. It will work perfectly > fine with virtually mapped pages. > > Replace the kmalloc() call by kvmalloc() and provide a __kvzfree() > helper function to clear and free the kvmalloc'ed buffer. This will > reduce the chance of memory allocation failure just because of highly > fragmented pages. > > Suggested-by: David Howells <dhowells@redhat.com> > Signed-off-by: Waiman Long <longman@redhat.com> > --- > security/keys/internal.h | 14 ++++++++++++++ > security/keys/keyctl.c | 10 +++++----- > 2 files changed, 19 insertions(+), 5 deletions(-) > > diff --git a/security/keys/internal.h b/security/keys/internal.h > index ba3e2da14cef..855b11eb73ee 100644 > --- a/security/keys/internal.h > +++ b/security/keys/internal.h > @@ -16,6 +16,8 @@ > #include <linux/keyctl.h> > #include <linux/refcount.h> > #include <linux/compat.h> > +#include <linux/mm.h> > +#include <linux/vmalloc.h> > > struct iovec; > > @@ -349,4 +351,16 @@ static inline void key_check(const struct key *key) > > #endif > > +/* > + * Helper function to clear and free a kvmalloc'ed memory object. > + */ > +static inline void __kvzfree(const void *addr, size_t len) > +{ > + if (is_vmalloc_addr(addr)) { > + memset((void *)addr, 0, len); > + vfree(addr); > + } else { > + kzfree(addr); > + } > +}
Since this takes the length as a parameter, it can be simplified to:
static inline void __kvzfree(const void *addr, size_t len) { if (addr) { memset((void *)addr, 0, len); kvfree(addr); } }
> if (!tmpbuf || unlikely(ret > tmpbuflen)) { > if (unlikely(tmpbuf)) > - kzfree(tmpbuf); > + __kvzfree(tmpbuf, tmpbuflen);
Both kzfree() and __kvzfree() handle a NULL pointer, so there's no need for the NULL check first.
> @@ -920,7 +920,7 @@ long keyctl_read_key(key_serial_t keyid, char __user *buffer, size_t buflen) > ret = -EFAULT; > } > if (tmpbuf) > - kzfree(tmpbuf); > + __kvzfree(tmpbuf, tmpbuflen);
Likewise here. No need for the NULL check.
- Eric
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