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| author | Jeremy Cline <jcline@redhat.com> | 2018-08-02 07:03:40 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-08-24 14:12:41 +0300 |
| commit | 51ada11083605de581b3c29212b5641d18cc8fcb (patch) | |
| tree | 169d6658809ef0b16d9d5074dd413b2f75473ce4 /fs/ext4 | |
| parent | 1cd0c7d732b9e59449ef57daf245bbfafa956601 (diff) | |
| download | linux-51ada11083605de581b3c29212b5641d18cc8fcb.tar.xz | |
ext4: fix spectre gadget in ext4_mb_regular_allocator()
commit 1a5d5e5d51e75a5bca67dadbcea8c841934b7b85 upstream.
'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
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs/ext4')
| -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 53e1890660a2..a49d0e5d7baf 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -26,6 +26,7 @@ #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> @@ -2144,7 +2145,8 @@ 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 */ |