diff options
| author | Jeremy Cline <jcline@redhat.com> | 2018-08-02 00:03:40 -0400 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2018-08-02 00:03:40 -0400 |
| commit | 1a5d5e5d51e75a5bca67dadbcea8c841934b7b85 (patch) | |
| tree | 5e6473b8361d5d4e9bd9caae0c282dc0eeed35fc | |
| parent | 7d95178c77014dbd8dce36ee40bbbc5e6c121ff5 (diff) | |
ext4: fix spectre gadget in ext4_mb_regular_allocator()
'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)
Suggested-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Jeremy Cline <jcline@redhat.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org
| -rw-r--r-- | fs/ext4/mballoc.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index f7ab34088162..8b24d3d42cb3 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -14,6 +14,7 @@ #include <linux/log2.h> #include <linux/module.h> #include <linux/slab.h> +#include <linux/nospec.h> #include <linux/backing-dev.h> #include <trace/events/ext4.h> @@ -2140,7 +2141,8 @@ ext4_mb_regular_allocator(struct ext4_allocation_context *ac) * This should tell if fe_len is exactly power of 2 */ if ((ac->ac_g_ex.fe_len & (~(1 << (i - 1)))) == 0) - ac->ac_2order = i - 1; + ac->ac_2order = array_index_nospec(i - 1, + sb->s_blocksize_bits + 2); } /* if stream allocation is enabled, use global goal */ |