First of all thanks for catching this. Yeah, I think the right thing to do here is to return the return value up to the caller. Also, I agree with Lukas, we should only set fc_modified_inodes_size if the allocation succeeds. Luo, would you be okay updating the patch to include these changes? Thanks, Harshad On Thu, Jan 6, 2022 at 2:58 AM Lukas Czerner <lczerner@xxxxxxxxxx> wrote: > > On Wed, Jan 05, 2022 at 11:44:39PM -0500, Theodore Ts'o wrote: > > On Thu, Dec 30, 2021 at 06:29:05AM +0000, cgel.zte@xxxxxxxxx wrote: > > > From: luo penghao <luo.penghao@xxxxxxxxxx> > > > > > > The assignments in these two places will be overwritten by new > > > assignments later, so they should be deleted. > > > > > > The clang_analyzer complains as follows: > > > > > > fs/ext4/fast_commit.c > > > > > > Value stored to 'ret' is never read > > > > I suspect the right answer here is that we *should* be checking the > > return value, and reflecting the error up to caller, if appropriate. > > > > Harshad, what do you think? > > Indeed we absolutely *must* be checking the return value and bail out > otherwise we risk overwriting kernel memory among other possible > problems. > > See ext4_fc_record_modified_inode() where we increment > fc_modified_inodes_size before the actual reallocation which in case of > allocation failure will leave us with elevated fc_modified_inodes_size > and the next call to ext4_fc_record_modified_inode() can modify > fc_modified_inodes[] out of bounds. > > In addition to checking the return value we should probably also move > incrementing the fc_modified_inodes_size until after the successful > reallocation in order to avoid such pitfalls. > > Thanks! > -Lukas > > > > > - Ted > > > > > > > > Reported-by: Zeal Robot <zealci@xxxxxxxxxx> > > > Signed-off-by: luo penghao <luo.penghao@xxxxxxxxxx> > > > --- > > > fs/ext4/fast_commit.c | 4 ++-- > > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > > > diff --git a/fs/ext4/fast_commit.c b/fs/ext4/fast_commit.c > > > index 8ea5a81..8d5d044 100644 > > > --- a/fs/ext4/fast_commit.c > > > +++ b/fs/ext4/fast_commit.c > > > @@ -1660,7 +1660,7 @@ static int ext4_fc_replay_add_range(struct super_block *sb, > > > return 0; > > > } > > > > > > - ret = ext4_fc_record_modified_inode(sb, inode->i_ino); > > > + ext4_fc_record_modified_inode(sb, inode->i_ino); > > > > > > start = le32_to_cpu(ex->ee_block); > > > start_pblk = ext4_ext_pblock(ex); > > > @@ -1785,7 +1785,7 @@ ext4_fc_replay_del_range(struct super_block *sb, struct ext4_fc_tl *tl, > > > return 0; > > > } > > > > > > - ret = ext4_fc_record_modified_inode(sb, inode->i_ino); > > > + ext4_fc_record_modified_inode(sb, inode->i_ino); > > > > > > jbd_debug(1, "DEL_RANGE, inode %ld, lblk %d, len %d\n", > > > inode->i_ino, le32_to_cpu(lrange.fc_lblk), > > > -- > > > 2.15.2 > > > > > > > > >
