From: David Howells dhowells@redhat.com
[ Upstream commit a635415a064e77bcfbf43da413fd9dfe0bbed9cb ]
In watch_queue_set_size(), the error cleanup code doesn't take account of the fact that __free_page() can't handle a NULL pointer when trying to free up buffer pages that did get allocated.
Fix this by only calling __free_page() on the pages actually allocated.
Without the fix, this can lead to something like the following:
BUG: KASAN: null-ptr-deref in __free_pages+0x1f/0x1b0 mm/page_alloc.c:5473 Read of size 4 at addr 0000000000000034 by task syz-executor168/3599 ... Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 __kasan_report mm/kasan/report.c:446 [inline] kasan_report.cold+0x66/0xdf mm/kasan/report.c:459 check_region_inline mm/kasan/generic.c:183 [inline] kasan_check_range+0x13d/0x180 mm/kasan/generic.c:189 instrument_atomic_read include/linux/instrumented.h:71 [inline] atomic_read include/linux/atomic/atomic-instrumented.h:27 [inline] page_ref_count include/linux/page_ref.h:67 [inline] put_page_testzero include/linux/mm.h:717 [inline] __free_pages+0x1f/0x1b0 mm/page_alloc.c:5473 watch_queue_set_size+0x499/0x630 kernel/watch_queue.c:275 pipe_ioctl+0xac/0x2b0 fs/pipe.c:632 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:874 [inline] __se_sys_ioctl fs/ioctl.c:860 [inline] __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:860 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae
Fixes: c73be61cede5 ("pipe: Add general notification queue support") Reported-and-tested-by: syzbot+d55757faa9b80590767b@syzkaller.appspotmail.com Signed-off-by: David Howells dhowells@redhat.com Reviewed-by: Fabio M. De Francesco fmdefrancesco@gmail.com Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/watch_queue.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/watch_queue.c b/kernel/watch_queue.c index 00703444a219..5848d4795816 100644 --- a/kernel/watch_queue.c +++ b/kernel/watch_queue.c @@ -271,7 +271,7 @@ long watch_queue_set_size(struct pipe_inode_info *pipe, unsigned int nr_notes) return 0;
error_p: - for (i = 0; i < nr_pages; i++) + while (--i >= 0) __free_page(pages[i]); kfree(pages); error: