Messages in this thread Patch in this message | | | From | Andreas Gruenbacher <> | Date | Tue, 28 Mar 2023 01:10:31 +0200 | Subject | Re: [PATCH] gfs2 FS: Fix UBSAN array-index-out-of-bounds in __gfs2_iomap_get |
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Hello Ivan,
On Wed, Mar 15, 2023 at 10:06 AM Ivan Orlov <ivan.orlov0322@gmail.com> wrote: > Syzkaller reported the following issue: > > UBSAN: array-index-out-of-bounds in fs/gfs2/bmap.c:901:46 > index 11 is out of range for type 'u64 [11]' > CPU: 0 PID: 5067 Comm: syz-executor164 Not tainted 6.1.0-syzkaller-13031-g77856d911a8c #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022 > Call Trace: > <TASK> > __dump_stack lib/dump_stack.c:88 [inline] > dump_stack_lvl+0x1b1/0x290 lib/dump_stack.c:106 > ubsan_epilogue lib/ubsan.c:151 [inline] > __ubsan_handle_out_of_bounds+0xe0/0x110 lib/ubsan.c:282 > __gfs2_iomap_get+0x4a4/0x16e0 fs/gfs2/bmap.c:901 > gfs2_iomap_get fs/gfs2/bmap.c:1399 [inline] > gfs2_block_map+0x28f/0x7f0 fs/gfs2/bmap.c:1214 > gfs2_write_alloc_required+0x441/0x6e0 fs/gfs2/bmap.c:2322 > gfs2_jdesc_check+0x1b9/0x290 fs/gfs2/super.c:114 > init_journal+0x5a4/0x22c0 fs/gfs2/ops_fstype.c:804 > init_inodes+0xdc/0x340 fs/gfs2/ops_fstype.c:889 > gfs2_fill_super+0x1bb2/0x2700 fs/gfs2/ops_fstype.c:1247 > get_tree_bdev+0x400/0x620 fs/super.c:1282 > gfs2_get_tree+0x50/0x210 fs/gfs2/ops_fstype.c:1330 > vfs_get_tree+0x88/0x270 fs/super.c:1489 > do_new_mount+0x289/0xad0 fs/namespace.c:3145 > do_mount fs/namespace.c:3488 [inline] > __do_sys_mount fs/namespace.c:3697 [inline] > __se_sys_mount+0x2d3/0x3c0 fs/namespace.c:3674 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x63/0xcd > RIP: 0033:0x7f2c63567aca > Code: 83 c4 08 5b 5d c3 66 2e 0f 1f 84 00 00 00 00 00 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48 > RSP: 002b:00007ffd0e3a28d8 EFLAGS: 00000282 ORIG_RAX: 00000000000000a5 > RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f2c63567aca > RDX: 0000000020037f40 RSI: 0000000020037f80 RDI: 00007ffd0e3a28e0 > RBP: 00007ffd0e3a28e0 R08: 00007ffd0e3a2920 R09: 0000000000043350 > R10: 0000000002000011 R11: 0000000000000282 R12: 0000000000000004 > R13: 00005555567192c0 R14: 00007ffd0e3a2920 R15: 0000000000000000 > </TASK> > > This issue is caused by the 'while' loop in the '__gfs2_iomap_get' function, > which increments 'height' var until it matches the condition. If height is > larger or equal to 'sdp->sd_heightsize' array size (which is GFS2_MAX_META_HEIGHT > + 1), the array-index-out-of-bounds issue occurs. Therefore we need to add extra > condition to the while loop, which will prevent this issue. > > Additionally, if 'height' var after the while ending is equal to GFS2_MAX_META_HEIGHT, > the 'find_metapath' call right after the loop will break (because it assumes that > 'height' parameter will not be larger than the size of metapath's mp_list array length, > which is GFS2_MAX_META_HEIGHT). So, we need to check the 'height' after the loop ending, > and if its value is too big we need to break the execution of the function, and return > a proper error if it is too big.
Thanks for the patch, but the actual problem here is that we're starting out with an invalid height; when starting with a valid height, the loop will always terminate. Here's a proper fix:
https://listman.redhat.com/archives/cluster-devel/2023-March/023644.html
While looking into this, I had difficulties getting prepro.c to work. The reason is that it always uses /dev/loop0 instead of creating its own loop device. Here's a partial fix for that (but note that this doesn't include the necessary cleanup code at the end):
--- a/repro.c +++ b/repro.c @@ -26,8 +26,6 @@ #define __NR_memfd_create 319 #endif
-static unsigned long long procid; - //% This code is derived from puff.{c,h}, found in the zlib development. The //% original files come with the following copyright notice:
@@ -423,8 +421,15 @@ static long syz_mount_image(volatile long fsarg, volatile long dir, char* source = NULL; char loopname[64]; if (need_loop_device) { + int loopctlfd; + long devnr; + + loopctlfd = open("/dev/loop-control", O_RDWR); + devnr = ioctl(loopctlfd, LOOP_CTL_GET_FREE); + close(loopctlfd); + memset(loopname, 0, sizeof(loopname)); - snprintf(loopname, sizeof(loopname), "/dev/loop%llu", procid); + snprintf(loopname, sizeof(loopname), "/dev/loop%lu", devnr); if (setup_loop_device(data, size, loopname, &loopfd) == -1) return -1; source = loopname; Thanks, Andreas
> Tested via syzbot. > > Reported-by: syzbot+45d4691b1ed3c48eba05@syzkaller.appspotmail.com > Link: https://syzkaller.appspot.com/bug?id=42296ea544c870f4dde3b25efa4cc1b89515d38e > Signed-off-by: Ivan Orlov <ivan.orlov0322@gmail.com> > --- > fs/gfs2/bmap.c | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) > > diff --git a/fs/gfs2/bmap.c b/fs/gfs2/bmap.c > index eedf6926c652..9b7358165f96 100644 > --- a/fs/gfs2/bmap.c > +++ b/fs/gfs2/bmap.c > @@ -895,8 +895,16 @@ static int __gfs2_iomap_get(struct inode *inode, loff_t pos, loff_t length, > iomap->length = len << inode->i_blkbits; > > height = ip->i_height; > - while ((lblock + 1) * sdp->sd_sb.sb_bsize > sdp->sd_heightsize[height]) > + > + while (height <= GFS2_MAX_META_HEIGHT > + && (lblock + 1) * sdp->sd_sb.sb_bsize > sdp->sd_heightsize[height]) > height++; > + > + if (height > GFS2_MAX_META_HEIGHT) { > + ret = -ERANGE; > + goto unlock; > + } > + > find_metapath(sdp, lblock, mp, height); > if (height > ip->i_height || gfs2_is_stuffed(ip)) > goto do_alloc; > -- > 2.34.1 >
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