On Fri 27-05-16 13:31:50, Andrew Morton wrote: > From: Arnd Bergmann <arnd@xxxxxxxx> > Subject: reiserfs: avoid uninitialized variable use > > I got this warning on an ARM64 allmodconfig build with gcc-5.3: > > fs/reiserfs/ibalance.c: In function 'balance_internal': > fs/reiserfs/ibalance.c:1158:3: error: 'new_insert_key' may be used uninitialized in this function [-Werror=maybe-uninitialized] > memcpy(new_insert_key_addr, &new_insert_key, KEY_SIZE); > > The warning is correct, in fact both new_insert_key and new_insert_ptr are > only updated inside of an if() block, but used at the end of the function. > > Looking at how the balance_internal() function gets called, it is clear > that this is harmless because the caller never uses the updated arrays, > they are initialized from balance_leaf_new_nodes() and then passed into > balance_internal(). > > This has not changed at all since the start of the git history, but > apparently the warning has only recently appeared. > > This modifies the function to only update the two argument variables when > the new_insert_key and new_insert_ptr have been updated, to get rid of the > warning. > > Link: http://lkml.kernel.org/r/1464380569-3493380-1-git-send-email-arnd@xxxxxxxx > Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx> > Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx> > Cc: Jan Kara <jack@xxxxxxx> > Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > --- > > fs/reiserfs/ibalance.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff -puN fs/reiserfs/ibalance.c~reiserfs-avoid-uninitialized-variable-use fs/reiserfs/ibalance.c > --- a/fs/reiserfs/ibalance.c~reiserfs-avoid-uninitialized-variable-use > +++ a/fs/reiserfs/ibalance.c > @@ -1138,6 +1138,9 @@ int balance_internal(struct tree_balance > S_new); > > /* S_new is released in unfix_nodes */ > + > + memcpy(new_insert_key_addr, &new_insert_key, KEY_SIZE); > + insert_ptr[0] = new_insert_ptr; > } > > n = B_NR_ITEMS(tbSh); /*number of items in S[h] */ > @@ -1153,8 +1156,5 @@ int balance_internal(struct tree_balance > insert_ptr); > } > > - memcpy(new_insert_key_addr, &new_insert_key, KEY_SIZE); > - insert_ptr[0] = new_insert_ptr; > - > return order; > } Looking at the patch now, I think it is buggy. The insert_ptr is used as an argument to internal_insert_childs() and this patch ends up overwriting the original value before the last call to that function... Not that I would really understand what the code is trying to do (CCed Jeff who may have better idea), this is based purely on syntactical analysis ;). Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe reiserfs-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
