Messages in this thread | | | Date | Thu, 26 Jan 2023 00:31:56 +0900 | From | Shigeru Yoshida <> | Subject | Re: [PATCH -next] udf: Fix a race condition between udf_rename() and udf_expand_dir_adinicb() |
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Hi Jan,
On Wed, Jan 25, 2023 at 10:16:13AM +0100, Jan Kara wrote: > On Wed 25-01-23 02:30:15, Shigeru Yoshida wrote: > > syzbot reported a general fault in udf_filter_write_fi() [1]. This > > causes a stack trace like below: > > > > general protection fault, probably for non-canonical address 0xdffffc0000000005: 0000 [#1] PREEMPT SMP KASAN > > KASAN: null-ptr-deref in range [0x0000000000000028-0x000000000000002f] > > CPU: 0 PID: 5127 Comm: syz-executor298 Not tainted 6.2.0-rc3-next-20230112-syzkaller #0 > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022 > > RIP: 0010:udf_fiiter_write_fi+0x14e/0x9d0 fs/udf/directory.c:402 > > ... > > Call Trace: > > <TASK> > > udf_rename+0x69d/0xb80 fs/udf/namei.c:874 > > vfs_rename+0x1162/0x1a90 fs/namei.c:4780 > > do_renameat2+0xb22/0xc30 fs/namei.c:4931 > > __do_sys_rename fs/namei.c:4977 [inline] > > __se_sys_rename fs/namei.c:4975 [inline] > > __x64_sys_rename+0x81/0xa0 fs/namei.c:4975 > > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > > do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80 > > entry_SYSCALL_64_after_hwframe+0x63/0xcd > > > > The cause of this issue is a race condition between udf_rename() and > > udf_expand_dir_adinicb(). > > > > If udf_rename() and udf_expand_dir_adinicb() run concurrently, > > iinfo->i_alloc_type can be changed by udf_expand_dir_adinicb() while > > udf_rename() is running. This causes NULL pointer dereference for > > iter->bh[0]->b_data in udf_fiiter_write_fi(). > > > > Link: https://syzkaller.appspot.com/bug?id=2811e6cdd35ea1df1fa2ef31b8d92c6408aa15d2 [1] > > Reported-by: syzbot+aebf90eea2671c43112a@syzkaller.appspotmail.com > > Signed-off-by: Shigeru Yoshida <syoshida@redhat.com> > > Thanks for the patch but I have already fixed the bug in a patch I've > posted here [1]. A cleaner fix is actually to use i_rwsem to protect moved > directory from other modifications (which is what I did).
Thanks for your feedback. I've missed the patch you mentioned and your patch is more elegant than mine.
Thank you~ Shigeru
> > [1] https://lore.kernel.org/all/20230124121814.25951-14-jack@suse.cz > > Honza > > > --- > > fs/udf/namei.c | 35 ++++++++++++++++++++++++----------- > > 1 file changed, 24 insertions(+), 11 deletions(-) > > > > diff --git a/fs/udf/namei.c b/fs/udf/namei.c > > index 06f066ba3072..5048652c6cd4 100644 > > --- a/fs/udf/namei.c > > +++ b/fs/udf/namei.c > > @@ -149,6 +149,8 @@ static struct buffer_head *udf_expand_dir_adinicb(struct inode *inode, > > uint8_t *impuse; > > int ret; > > > > + down_write(&iinfo->i_data_sem); > > + > > if (UDF_QUERY_FLAG(inode->i_sb, UDF_FLAG_USE_SHORT_AD)) > > alloctype = ICBTAG_FLAG_AD_SHORT; > > else > > @@ -157,7 +159,7 @@ static struct buffer_head *udf_expand_dir_adinicb(struct inode *inode, > > if (!inode->i_size) { > > iinfo->i_alloc_type = alloctype; > > mark_inode_dirty(inode); > > - return NULL; > > + goto out; > > } > > > > /* alloc block, and copy data to it */ > > @@ -165,15 +167,15 @@ static struct buffer_head *udf_expand_dir_adinicb(struct inode *inode, > > iinfo->i_location.partitionReferenceNum, > > iinfo->i_location.logicalBlockNum, err); > > if (!(*block)) > > - return NULL; > > + goto out; > > newblock = udf_get_pblock(inode->i_sb, *block, > > iinfo->i_location.partitionReferenceNum, > > 0); > > if (!newblock) > > - return NULL; > > + goto out; > > dbh = udf_tgetblk(inode->i_sb, newblock); > > if (!dbh) > > - return NULL; > > + goto out; > > lock_buffer(dbh); > > memcpy(dbh->b_data, iinfo->i_data, inode->i_size); > > memset(dbh->b_data + inode->i_size, 0, > > @@ -197,7 +199,7 @@ static struct buffer_head *udf_expand_dir_adinicb(struct inode *inode, > > if (ret < 0) { > > *err = ret; > > udf_free_blocks(inode->i_sb, inode, &eloc, 0, 1); > > - return NULL; > > + goto out; > > } > > mark_inode_dirty(inode); > > > > @@ -213,6 +215,8 @@ static struct buffer_head *udf_expand_dir_adinicb(struct inode *inode, > > impuse = NULL; > > udf_fiiter_write_fi(&iter, impuse); > > } > > + up_write(&iinfo->i_data_sem); > > + > > /* > > * We don't expect the iteration to fail as the directory has been > > * already verified to be correct > > @@ -221,6 +225,9 @@ static struct buffer_head *udf_expand_dir_adinicb(struct inode *inode, > > udf_fiiter_release(&iter); > > > > return dbh; > > +out: > > + up_write(&iinfo->i_data_sem); > > + return NULL; > > } > > > > static int udf_fiiter_add_entry(struct inode *dir, struct dentry *dentry, > > @@ -766,6 +773,7 @@ static int udf_rename(struct mnt_idmap *idmap, struct inode *old_dir, > > bool has_diriter = false; > > int retval; > > struct kernel_lb_addr tloc; > > + struct udf_inode_info *old_iinfo = UDF_I(old_inode); > > > > if (flags & ~RENAME_NOREPLACE) > > return -EINVAL; > > @@ -780,11 +788,13 @@ static int udf_rename(struct mnt_idmap *idmap, struct inode *old_dir, > > goto out_oiter; > > } > > > > + down_read(&old_iinfo->i_data_sem); > > + > > if (S_ISDIR(old_inode->i_mode)) { > > if (new_inode) { > > retval = -ENOTEMPTY; > > if (!empty_dir(new_inode)) > > - goto out_oiter; > > + goto out_unlock; > > } > > retval = udf_fiiter_find_entry(old_inode, &dotdot_name, > > &diriter); > > @@ -795,7 +805,7 @@ static int udf_rename(struct mnt_idmap *idmap, struct inode *old_dir, > > retval = -EFSCORRUPTED; > > } > > if (retval) > > - goto out_oiter; > > + goto out_unlock; > > has_diriter = true; > > tloc = lelb_to_cpu(diriter.fi.icb.extLocation); > > if (udf_get_lb_pblock(old_inode->i_sb, &tloc, 0) != > > @@ -805,25 +815,25 @@ static int udf_rename(struct mnt_idmap *idmap, struct inode *old_dir, > > "directory (ino %lu) has parent entry pointing to another inode (%lu != %u)\n", > > old_inode->i_ino, old_dir->i_ino, > > udf_get_lb_pblock(old_inode->i_sb, &tloc, 0)); > > - goto out_oiter; > > + goto out_unlock; > > } > > } > > > > retval = udf_fiiter_find_entry(new_dir, &new_dentry->d_name, &niter); > > if (retval && retval != -ENOENT) > > - goto out_oiter; > > + goto out_unlock; > > /* Entry found but not passed by VFS? */ > > if (!retval && !new_inode) { > > retval = -EFSCORRUPTED; > > udf_fiiter_release(&niter); > > - goto out_oiter; > > + goto out_unlock; > > } > > /* Entry not found? Need to add one... */ > > if (retval) { > > udf_fiiter_release(&niter); > > retval = udf_fiiter_add_entry(new_dir, new_dentry, &niter); > > if (retval) > > - goto out_oiter; > > + goto out_unlock; > > } > > > > /* > > @@ -882,7 +892,10 @@ static int udf_rename(struct mnt_idmap *idmap, struct inode *old_dir, > > mark_inode_dirty(new_dir); > > } > > } > > + up_read(&old_iinfo->i_data_sem); > > return 0; > > +out_unlock: > > + up_read(&old_iinfo->i_data_sem); > > out_oiter: > > if (has_diriter) > > udf_fiiter_release(&diriter); > > -- > > 2.39.0 > > > -- > Jan Kara <jack@suse.com> > SUSE Labs, CR >
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