On Tue, Jul 14, 2020 at 06:05:09AM -0700, [email protected] wrote: > From: Tom Rix <[email protected]> > > clang static analysis flags this error > > inode.c:1083:5: warning: Argument to kfree() is the address of the > local variable 'unf_single', which is not memory allocated by > malloc() [unix.Malloc] > kfree(un); > ^~~~~~~~~ > Assignment of 'un' > > /* > * We use this in case we need to allocate > * only one block which is a fastpath > */ > unp_t unf_single = 0; > > ... > > if (blocks_needed == 1) { > un = &unf_single; > } else { > un = kcalloc(min(blocks_needed, max_to_insert), > UNFM_P_SIZE, GFP_NOFS); > if (!un) { > un = &unf_single; > blocks_needed = 1; > max_to_insert = 0; > } > } > > The logic to free 'un' > > if (blocks_needed != 1) > kfree(un); > > Because the kcalloc failure falls back to using unf_single, > the if-check for the free is wrong.
I think you mean "Because clang's static analysis is limited, it warns incorrectly about this". There's no path to get to the kfree with blocks_needed != 1 and un being equal to &unf_single. > So improve the check. > > Signed-off-by: Tom Rix <[email protected]> > --- > fs/reiserfs/inode.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/reiserfs/inode.c b/fs/reiserfs/inode.c > index 1509775da040..4d62148e43e6 100644 > --- a/fs/reiserfs/inode.c > +++ b/fs/reiserfs/inode.c > @@ -1079,7 +1079,7 @@ int reiserfs_get_block(struct inode *inode, sector_t > block, > UNFM_P_SIZE * > blocks_needed); > > - if (blocks_needed != 1) > + if (un != &unf_single) > kfree(un); I don't actually object to this patch, but your analysis of clang's analysis is wrong.
