diff options
| author | Qian Cai <cai@lca.pw> | 2020-04-02 07:06:13 +0300 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-04-02 19:35:27 +0300 |
| commit | 218209487c3da2f6d861b236c11226b6eca7b7b7 (patch) | |
| tree | 1c62d68fbb6569f08d3365697df6a407962fdf44 | |
| parent | bde07cfc65da5fe6c63fe23f035f5ccc0ffd89e0 (diff) | |
| download | linux-218209487c3da2f6d861b236c11226b6eca7b7b7.tar.xz | |
mm/swapfile: fix data races in try_to_unuse()
si->inuse_pages could be accessed concurrently as noticed by KCSAN,
write to 0xffff98b00ebd04dc of 4 bytes by task 82262 on cpu 92:
swap_range_free+0xbe/0x230
swap_range_free at mm/swapfile.c:719
swapcache_free_entries+0x1be/0x250
free_swap_slot+0x1c8/0x220
__swap_entry_free.constprop.19+0xa3/0xb0
free_swap_and_cache+0x53/0xa0
unmap_page_range+0x7e0/0x1ce0
unmap_single_vma+0xcd/0x170
unmap_vmas+0x18b/0x220
exit_mmap+0xee/0x220
mmput+0xe7/0x240
do_exit+0x598/0xfd0
do_group_exit+0x8b/0x180
get_signal+0x293/0x13d0
do_signal+0x37/0x5d0
prepare_exit_to_usermode+0x1b7/0x2c0
ret_from_intr+0x32/0x42
read to 0xffff98b00ebd04dc of 4 bytes by task 82499 on cpu 46:
try_to_unuse+0x86b/0xc80
try_to_unuse at mm/swapfile.c:2185
__x64_sys_swapoff+0x372/0xd40
do_syscall_64+0x91/0xb05
entry_SYSCALL_64_after_hwframe+0x49/0xbe
The plain reads in try_to_unuse() are outside si->lock critical section
which result in data races that could be dangerous to be used in a loop.
Fix them by adding READ_ONCE().
Signed-off-by: Qian Cai <cai@lca.pw>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Marco Elver <elver@google.com>
Cc: Hugh Dickins <hughd@google.com>
Link: http://lkml.kernel.org/r/1582578903-29294-1-git-send-email-cai@lca.pw
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | mm/swapfile.c | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/mm/swapfile.c b/mm/swapfile.c index 6d63bd9b7da2..273a923c275c 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -2132,7 +2132,7 @@ int try_to_unuse(unsigned int type, bool frontswap, swp_entry_t entry; unsigned int i; - if (!si->inuse_pages) + if (!READ_ONCE(si->inuse_pages)) return 0; if (!frontswap) @@ -2148,7 +2148,7 @@ retry: spin_lock(&mmlist_lock); p = &init_mm.mmlist; - while (si->inuse_pages && + while (READ_ONCE(si->inuse_pages) && !signal_pending(current) && (p = p->next) != &init_mm.mmlist) { @@ -2177,7 +2177,7 @@ retry: mmput(prev_mm); i = 0; - while (si->inuse_pages && + while (READ_ONCE(si->inuse_pages) && !signal_pending(current) && (i = find_next_to_unuse(si, i, frontswap)) != 0) { @@ -2219,7 +2219,7 @@ retry: * been preempted after get_swap_page(), temporarily hiding that swap. * It's easy and robust (though cpu-intensive) just to keep retrying. */ - if (si->inuse_pages) { + if (READ_ONCE(si->inuse_pages)) { if (!signal_pending(current)) goto retry; retval = -EINTR; |