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ext4: check for directory entries too close to block end 

commit 109ba779d6 upstream.

ext4_check_dir_entry() currently does not catch a case when a directory
entry ends so close to the block end that the header of the next
directory entry would not fit in the remaining space. This can lead to
directory iteration code trying to access address beyond end of current
buffer head leading to oops.

CC: stable@vger.kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20191202170213.4761-3-jack@suse.cz
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jan Kara 2019-12-02 18:02:13 +01:00 committed by Greg Kroah-Hartman
parent 6cc4ccdd0b
commit 6f63704838
1 changed files with 5 additions and 0 deletions
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5
fs/ext4/dir.c
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@ -81,6 +81,11 @@ int __ext4_check_dir_entry(const char *function, unsigned int line,
error_msg = "rec_len is too small for name_len";
else if (unlikely(((char *) de - buf) + rlen > size))
error_msg = "directory entry overrun";
else if (unlikely(((char *) de - buf) + rlen >
size - EXT4_DIR_REC_LEN(1) &&
((char *) de - buf) + rlen != size)) {
error_msg = "directory entry too close to block end";
}
else if (unlikely(le32_to_cpu(de->inode) >
le32_to_cpu(EXT4_SB(dir->i_sb)->s_es->s_inodes_count)))
error_msg = "inode out of bounds";