Re: [PATCH] iov_iter: fix memleak in iov_iter_extract_pages

From: José Pekkarinen
Date: Mon Nov 20 2023 - 10:37:14 EST

On 2023-11-11 09:53, José Pekkarinen wrote:
syzbot reports there is a memory leak in iov_iter_extract_pages where in
the unlikely case of having an error in pin_user_pages_fast, the pages
aren't free. This patch will free it before returning. Output of mem
leak follows:

BUG: memory leak
unreferenced object 0xffff888109d2e400 (size 1024):
comm "syz-executor121", pid 5006, jiffies 4294943225 (age 17.760s)
hex dump (first 32 bytes):
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
backtrace:
[<ffffffff81554bbb>] __do_kmalloc_node mm/slab_common.c:984 [inline]
[<ffffffff81554bbb>] __kmalloc_node+0x4b/0x150 mm/slab_common.c:992
[<ffffffff815440f9>] kmalloc_node include/linux/slab.h:602 [inline]
[<ffffffff815440f9>] kvmalloc_node+0x99/0x170 mm/util.c:604
[<ffffffff824c52fe>] kvmalloc include/linux/slab.h:720 [inline]
[<ffffffff824c52fe>] kvmalloc_array include/linux/slab.h:738 [inline]
[<ffffffff824c52fe>] want_pages_array lib/iov_iter.c:985 [inline]
[<ffffffff824c52fe>] iov_iter_extract_user_pages
lib/iov_iter.c:1765 [inline]
[<ffffffff824c52fe>] iov_iter_extract_pages+0x1ee/0xa40 lib/iov_iter.c:1831
[<ffffffff824125a7>] bio_map_user_iov+0x167/0x5d0 block/blk-map.c:297
[<ffffffff82412df3>] blk_rq_map_user_iov+0x3e3/0xb30 block/blk-map.c:664
[<ffffffff82413943>] blk_rq_map_user block/blk-map.c:691 [inline]
[<ffffffff82413943>] blk_rq_map_user_io+0x143/0x160 block/blk-map.c:724
[<ffffffff82ca0925>] sg_io+0x285/0x510 drivers/scsi/scsi_ioctl.c:456
[<ffffffff82ca1025>] scsi_cdrom_send_packet+0x1b5/0x480
drivers/scsi/scsi_ioctl.c:820
[<ffffffff82ca13ba>] scsi_ioctl+0xca/0xd30 drivers/scsi/scsi_ioctl.c:903
[<ffffffff82d35964>] sg_ioctl+0x5f4/0x10a0 drivers/scsi/sg.c:1163
[<ffffffff8168e602>] vfs_ioctl fs/ioctl.c:51 [inline]
[<ffffffff8168e602>] __do_sys_ioctl fs/ioctl.c:870 [inline]
[<ffffffff8168e602>] __se_sys_ioctl fs/ioctl.c:856 [inline]
[<ffffffff8168e602>] __x64_sys_ioctl+0xf2/0x140 fs/ioctl.c:856
[<ffffffff84ad2bb8>] do_syscall_x64 arch/x86/entry/common.c:50 [inline]
[<ffffffff84ad2bb8>] do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80
[<ffffffff84c0008b>] entry_SYSCALL_64_after_hwframe+0x63/0xcd

BUG: memory leak
unreferenced object 0xffff888109d2dc00 (size 1024):
comm "syz-executor121", pid 5007, jiffies 4294943747 (age 12.540s)
hex dump (first 32 bytes):
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
backtrace:
[<ffffffff81554bbb>] __do_kmalloc_node mm/slab_common.c:984 [inline]
[<ffffffff81554bbb>] __kmalloc_node+0x4b/0x150 mm/slab_common.c:992
[<ffffffff815440f9>] kmalloc_node include/linux/slab.h:602 [inline]
[<ffffffff815440f9>] kvmalloc_node+0x99/0x170 mm/util.c:604
[<ffffffff824c52fe>] kvmalloc include/linux/slab.h:720 [inline]
[<ffffffff824c52fe>] kvmalloc_array include/linux/slab.h:738 [inline]
[<ffffffff824c52fe>] want_pages_array lib/iov_iter.c:985 [inline]
[<ffffffff824c52fe>] iov_iter_extract_user_pages
lib/iov_iter.c:1765 [inline]
[<ffffffff824c52fe>] iov_iter_extract_pages+0x1ee/0xa40 lib/iov_iter.c:1831
[<ffffffff824125a7>] bio_map_user_iov+0x167/0x5d0 block/blk-map.c:297
[<ffffffff82412df3>] blk_rq_map_user_iov+0x3e3/0xb30 block/blk-map.c:664
[<ffffffff82413943>] blk_rq_map_user block/blk-map.c:691 [inline]
[<ffffffff82413943>] blk_rq_map_user_io+0x143/0x160 block/blk-map.c:724
[<ffffffff82ca0925>] sg_io+0x285/0x510 drivers/scsi/scsi_ioctl.c:456
[<ffffffff82ca1025>] scsi_cdrom_send_packet+0x1b5/0x480
drivers/scsi/scsi_ioctl.c:820
[<ffffffff82ca13ba>] scsi_ioctl+0xca/0xd30 drivers/scsi/scsi_ioctl.c:903
[<ffffffff82d35964>] sg_ioctl+0x5f4/0x10a0 drivers/scsi/sg.c:1163
[<ffffffff8168e602>] vfs_ioctl fs/ioctl.c:51 [inline]
[<ffffffff8168e602>] __do_sys_ioctl fs/ioctl.c:870 [inline]
[<ffffffff8168e602>] __se_sys_ioctl fs/ioctl.c:856 [inline]
[<ffffffff8168e602>] __x64_sys_ioctl+0xf2/0x140 fs/ioctl.c:856
[<ffffffff84ad2bb8>] do_syscall_x64 arch/x86/entry/common.c:50 [inline]
[<ffffffff84ad2bb8>] do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80
[<ffffffff84c0008b>] entry_SYSCALL_64_after_hwframe+0x63/0xcd

BUG: memory leak
unreferenced object 0xffff888109d2d800 (size 1024):
comm "syz-executor121", pid 5010, jiffies 4294944269 (age 7.320s)
hex dump (first 32 bytes):
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
backtrace:
[<ffffffff81554bbb>] __do_kmalloc_node mm/slab_common.c:984 [inline]
[<ffffffff81554bbb>] __kmalloc_node+0x4b/0x150 mm/slab_common.c:992
[<ffffffff815440f9>] kmalloc_node include/linux/slab.h:602 [inline]
[<ffffffff815440f9>] kvmalloc_node+0x99/0x170 mm/util.c:604
[<ffffffff824c52fe>] kvmalloc include/linux/slab.h:720 [inline]
[<ffffffff824c52fe>] kvmalloc_array include/linux/slab.h:738 [inline]
[<ffffffff824c52fe>] want_pages_array lib/iov_iter.c:985 [inline]
[<ffffffff824c52fe>] iov_iter_extract_user_pages
lib/iov_iter.c:1765 [inline]
[<ffffffff824c52fe>] iov_iter_extract_pages+0x1ee/0xa40 lib/iov_iter.c:1831
[<ffffffff824125a7>] bio_map_user_iov+0x167/0x5d0 block/blk-map.c:297
[<ffffffff82412df3>] blk_rq_map_user_iov+0x3e3/0xb30 block/blk-map.c:664
[<ffffffff82413943>] blk_rq_map_user block/blk-map.c:691 [inline]
[<ffffffff82413943>] blk_rq_map_user_io+0x143/0x160 block/blk-map.c:724
[<ffffffff82ca0925>] sg_io+0x285/0x510 drivers/scsi/scsi_ioctl.c:456
[<ffffffff82ca1025>] scsi_cdrom_send_packet+0x1b5/0x480
drivers/scsi/scsi_ioctl.c:820
[<ffffffff82ca13ba>] scsi_ioctl+0xca/0xd30 drivers/scsi/scsi_ioctl.c:903
[<ffffffff82d35964>] sg_ioctl+0x5f4/0x10a0 drivers/scsi/sg.c:1163
[<ffffffff8168e602>] vfs_ioctl fs/ioctl.c:51 [inline]
[<ffffffff8168e602>] __do_sys_ioctl fs/ioctl.c:870 [inline]
[<ffffffff8168e602>] __se_sys_ioctl fs/ioctl.c:856 [inline]
[<ffffffff8168e602>] __x64_sys_ioctl+0xf2/0x140 fs/ioctl.c:856
[<ffffffff84ad2bb8>] do_syscall_x64 arch/x86/entry/common.c:50 [inline]
[<ffffffff84ad2bb8>] do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80
[<ffffffff84c0008b>] entry_SYSCALL_64_after_hwframe+0x63/0xcd

Reported-by: syzbot+cb729843d0f42a5c1a50@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes:
https://syzkaller.appspot.com/bug?id=99c8551967f413d108cfdd2950a0cb5652de07b8
Fixes: 7d58fe7310281 ("iov_iter: Add a function to extract a page list
from an iterator")
Signed-off-by: José Pekkarinen <jose.pekkarinen@xxxxxxxxxxx>
---
lib/iov_iter.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 27234a820eeb..c3fd0448dead 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -1780,8 +1780,10 @@ static ssize_t
iov_iter_extract_user_pages(struct iov_iter *i,
if (!maxpages)
return -ENOMEM;
res = pin_user_pages_fast(addr, maxpages, gup_flags, *pages);
- if (unlikely(res <= 0))
+ if (unlikely(res <= 0)) {
+ kvfree(*pages);
return res;
+ }
maxsize = min_t(size_t, maxsize, res * PAGE_SIZE - offset);
iov_iter_advance(i, maxsize);
return maxsize;

Ping.

José.