| Message ID | 720dcf79314acca1a78fae56d478cc851952149d.1637084492.git.christophe.leroy@csgroup.eu (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | gup: Avoid multiple user access locking/unlocking in fault_in_{read/write}able | expand |
On Tue, Nov 16, 2021 at 6:50 PM Christophe Leroy <christophe.leroy@csgroup.eu> wrote: > fault_in_readable() and fault_in_writeable() perform __get_user() > and __put_user() in a loop, implying multiple user access > locking/unlocking. > > To avoid that, use user access blocks. > > Cc: Andreas Gruenbacher <agruenba@redhat.com> > Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Reviewed-by: Andreas Gruenbacher <agruenba@redhat.com> > --- > mm/gup.c | 18 ++++++++++-------- > 1 file changed, 10 insertions(+), 8 deletions(-) > > diff --git a/mm/gup.c b/mm/gup.c > index 2c51e9748a6a..be2a41feec7d 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -1672,21 +1672,22 @@ size_t fault_in_writeable(char __user *uaddr, size_t size) > > if (unlikely(size == 0)) > return 0; > + if (!user_write_access_begin(uaddr, size)) > + return size; > if (!PAGE_ALIGNED(uaddr)) { > - if (unlikely(__put_user(0, uaddr) != 0)) > - return size; > + unsafe_put_user(0, uaddr, out); > uaddr = (char __user *)PAGE_ALIGN((unsigned long)uaddr); > } > end = (char __user *)PAGE_ALIGN((unsigned long)start + size); > if (unlikely(end < start)) > end = NULL; > while (uaddr != end) { > - if (unlikely(__put_user(0, uaddr) != 0)) > - goto out; > + unsafe_put_user(0, uaddr, out); > uaddr += PAGE_SIZE; > } > > out: > + user_write_access_end(); > if (size > uaddr - start) > return size - (uaddr - start); > return 0; > @@ -1771,21 +1772,22 @@ size_t fault_in_readable(const char __user *uaddr, size_t size) > > if (unlikely(size == 0)) > return 0; > + if (!user_read_access_begin(uaddr, size)) > + return size; > if (!PAGE_ALIGNED(uaddr)) { > - if (unlikely(__get_user(c, uaddr) != 0)) > - return size; > + unsafe_get_user(c, uaddr, out); > uaddr = (const char __user *)PAGE_ALIGN((unsigned long)uaddr); > } > end = (const char __user *)PAGE_ALIGN((unsigned long)start + size); > if (unlikely(end < start)) > end = NULL; > while (uaddr != end) { > - if (unlikely(__get_user(c, uaddr) != 0)) > - goto out; > + unsafe_get_user(c, uaddr, out); > uaddr += PAGE_SIZE; > } > > out: > + user_read_access_end(); > (void)c; > if (size > uaddr - start) > return size - (uaddr - start); > -- > 2.31.1 >
diff --git a/mm/gup.c b/mm/gup.c index 2c51e9748a6a..be2a41feec7d 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1672,21 +1672,22 @@ size_t fault_in_writeable(char __user *uaddr, size_t size) if (unlikely(size == 0)) return 0; + if (!user_write_access_begin(uaddr, size)) + return size; if (!PAGE_ALIGNED(uaddr)) { - if (unlikely(__put_user(0, uaddr) != 0)) - return size; + unsafe_put_user(0, uaddr, out); uaddr = (char __user *)PAGE_ALIGN((unsigned long)uaddr); } end = (char __user *)PAGE_ALIGN((unsigned long)start + size); if (unlikely(end < start)) end = NULL; while (uaddr != end) { - if (unlikely(__put_user(0, uaddr) != 0)) - goto out; + unsafe_put_user(0, uaddr, out); uaddr += PAGE_SIZE; } out: + user_write_access_end(); if (size > uaddr - start) return size - (uaddr - start); return 0; @@ -1771,21 +1772,22 @@ size_t fault_in_readable(const char __user *uaddr, size_t size) if (unlikely(size == 0)) return 0; + if (!user_read_access_begin(uaddr, size)) + return size; if (!PAGE_ALIGNED(uaddr)) { - if (unlikely(__get_user(c, uaddr) != 0)) - return size; + unsafe_get_user(c, uaddr, out); uaddr = (const char __user *)PAGE_ALIGN((unsigned long)uaddr); } end = (const char __user *)PAGE_ALIGN((unsigned long)start + size); if (unlikely(end < start)) end = NULL; while (uaddr != end) { - if (unlikely(__get_user(c, uaddr) != 0)) - goto out; + unsafe_get_user(c, uaddr, out); uaddr += PAGE_SIZE; } out: + user_read_access_end(); (void)c; if (size > uaddr - start) return size - (uaddr - start);
fault_in_readable() and fault_in_writeable() perform __get_user() and __put_user() in a loop, implying multiple user access locking/unlocking. To avoid that, use user access blocks. Cc: Andreas Gruenbacher <agruenba@redhat.com> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> --- mm/gup.c | 18 ++++++++++-------- 1 file changed, 10 insertions(+), 8 deletions(-)