Messages in this thread Patch in this message | | | From | Shigeru Yoshida <> | Subject | [PATCH -next] udf: Fix a race condition between udf_rename() and udf_expand_dir_adinicb() | Date | Wed, 25 Jan 2023 02:30:15 +0900 |
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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> --- 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
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