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authorChristophe Leroy <christophe.leroy@csgroup.eu>2022-01-15 01:05:13 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2022-01-15 17:30:26 +0300
commit677b2a8c1f25db5b09c1ef5bf72faa39ea81d9cf (patch)
tree663d5a0a7a5fade5b9edaeb0c7ef16fd320b0d23 /mm/gup.c
parent43b93121056c524e2af77d561900ea856d32029c (diff)
downloadlinux-677b2a8c1f25db5b09c1ef5bf72faa39ea81d9cf.tar.xz
gup: avoid multiple user access locking/unlocking in fault_in_{read/write}able
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. Link: https://lkml.kernel.org/r/720dcf79314acca1a78fae56d478cc851952149d.1637084492.git.christophe.leroy@csgroup.eu Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Reviewed-by: Andreas Gruenbacher <agruenba@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/gup.c')
-rw-r--r--mm/gup.c18
1 files 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);