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Message-Id: <20230124173015.3213309-1-syoshida@redhat.com>
Date: Wed, 25 Jan 2023 02:30:15 +0900
From: Shigeru Yoshida <syoshida@...hat.com>
To: jack@...e.com
Cc: linux-kernel@...r.kernel.org,
Shigeru Yoshida <syoshida@...hat.com>,
syzbot+aebf90eea2671c43112a@...kaller.appspotmail.com
Subject: [PATCH -next] udf: Fix a race condition between udf_rename() and udf_expand_dir_adinicb()
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@...kaller.appspotmail.com
Signed-off-by: Shigeru Yoshida <syoshida@...hat.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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