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[iov_iter] fix iterate_all_kinds() on empty iterators 

Problem similar to ones dealt with in "fold checks into iterate_and_advance()"
and followups, except that in this case we really want to do nothing when
asked for zero-length operation - unlike zero-length iterate_and_advance(),
zero-length iterate_all_kinds() has no side effects, and callers are simpler
that way.

That got exposed when copy_from_iter_full() had been used by tipc, which
builds an msghdr with zero payload and (now) feeds it to a primitive
based on iterate_all_kinds() instead of iterate_and_advance().

Reported-by: Jon Maloy <jon.maloy@ericsson.com>
Tested-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2016-12-21 21:55:02 -05:00
parent c00d2c7e89
commit 33844e6651
1 changed files with 26 additions and 29 deletions
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55
lib/iov_iter.c
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@ -73,19 +73,21 @@
}
#define iterate_all_kinds(i, n, v, I, B, K) { \
size_t skip = i->iov_offset; \
if (unlikely(i->type & ITER_BVEC)) { \
struct bio_vec v; \
struct bvec_iter __bi; \
iterate_bvec(i, n, v, __bi, skip, (B)) \
} else if (unlikely(i->type & ITER_KVEC)) { \
const struct kvec *kvec; \
struct kvec v; \
iterate_kvec(i, n, v, kvec, skip, (K)) \
} else { \
const struct iovec *iov; \
struct iovec v; \
iterate_iovec(i, n, v, iov, skip, (I)) \
if (likely(n)) { \
size_t skip = i->iov_offset; \
if (unlikely(i->type & ITER_BVEC)) { \
struct bio_vec v; \
struct bvec_iter __bi; \
iterate_bvec(i, n, v, __bi, skip, (B)) \
} else if (unlikely(i->type & ITER_KVEC)) { \
const struct kvec *kvec; \
struct kvec v; \
iterate_kvec(i, n, v, kvec, skip, (K)) \
} else { \
const struct iovec *iov; \
struct iovec v; \
iterate_iovec(i, n, v, iov, skip, (I)) \
} \
} \
}
@ -576,7 +578,7 @@ bool copy_from_iter_full(void *addr, size_t bytes, struct iov_iter *i)
WARN_ON(1);
return false;
}
if (unlikely(i->count < bytes)) \
if (unlikely(i->count < bytes))
return false;
iterate_all_kinds(i, bytes, v, ({
@ -620,7 +622,7 @@ bool copy_from_iter_full_nocache(void *addr, size_t bytes, struct iov_iter *i)
WARN_ON(1);
return false;
}
if (unlikely(i->count < bytes)) \
if (unlikely(i->count < bytes))
return false;
iterate_all_kinds(i, bytes, v, ({
if (__copy_from_user_nocache((to += v.iov_len) - v.iov_len,
@ -837,11 +839,8 @@ unsigned long iov_iter_alignment(const struct iov_iter *i)
unsigned long res = 0;
size_t size = i->count;
if (!size)
return 0;
if (unlikely(i->type & ITER_PIPE)) {
if (i->iov_offset && allocated(&i->pipe->bufs[i->idx]))
if (size && i->iov_offset && allocated(&i->pipe->bufs[i->idx]))
return size | i->iov_offset;
return size;
}
@ -856,10 +855,8 @@ EXPORT_SYMBOL(iov_iter_alignment);
unsigned long iov_iter_gap_alignment(const struct iov_iter *i)
{
unsigned long res = 0;
unsigned long res = 0;
size_t size = i->count;
if (!size)
return 0;
if (unlikely(i->type & ITER_PIPE)) {
WARN_ON(1);
@ -874,7 +871,7 @@ unsigned long iov_iter_gap_alignment(const struct iov_iter *i)
(res |= (!res ? 0 : (unsigned long)v.iov_base) |
(size != v.iov_len ? size : 0))
);
return res;
return res;
}
EXPORT_SYMBOL(iov_iter_gap_alignment);
@ -908,6 +905,9 @@ static ssize_t pipe_get_pages(struct iov_iter *i,
size_t capacity;
int idx;
if (!maxsize)
return 0;
if (!sanity(i))
return -EFAULT;
@ -926,9 +926,6 @@ ssize_t iov_iter_get_pages(struct iov_iter *i,
if (maxsize > i->count)
maxsize = i->count;
if (!maxsize)
return 0;
if (unlikely(i->type & ITER_PIPE))
return pipe_get_pages(i, pages, maxsize, maxpages, start);
iterate_all_kinds(i, maxsize, v, ({
@ -975,6 +972,9 @@ static ssize_t pipe_get_pages_alloc(struct iov_iter *i,
int idx;
int npages;
if (!maxsize)
return 0;
if (!sanity(i))
return -EFAULT;
@ -1006,9 +1006,6 @@ ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
if (maxsize > i->count)
maxsize = i->count;
if (!maxsize)
return 0;
if (unlikely(i->type & ITER_PIPE))
return pipe_get_pages_alloc(i, pages, maxsize, start);
iterate_all_kinds(i, maxsize, v, ({