On Mon, Jul 30, 2018 at 06:07:47PM +0000, Jeremy Cline wrote: > 'ac->ac_g_ex.fe_len' is a user-controlled value which is used in the > derivation of 'ac->ac_2order'. 'ac->ac_2order', in turn, is used to > index arrays which makes it a potential spectre gadget. Fix this by > sanitizing the value assigned to 'ac->ac2_order'. This covers the > following accesses found with the help of smatch: > > * fs/ext4/mballoc.c:1896 ext4_mb_simple_scan_group() warn: potential > spectre issue 'grp->bb_counters' [w] (local cap) > > * fs/ext4/mballoc.c:445 mb_find_buddy() warn: potential spectre issue > 'EXT4_SB(e4b->bd_sb)->s_mb_offsets' [r] (local cap) > > * fs/ext4/mballoc.c:446 mb_find_buddy() warn: potential spectre issue > 'EXT4_SB(e4b->bd_sb)->s_mb_maxs' [r] (local cap) > > Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> > Cc: stable@xxxxxxxxxxxxxxx > Suggested-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> > Signed-off-by: Jeremy Cline <jcline@xxxxxxxxxx> Reviewed-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> -- Josh
