lkml.org 
[lkml]   [2021]   [Oct]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 5.10 37/83] bpf: Fix integer overflow in prealloc_elems_and_freelist()
    Date
    From: Tatsuhiko Yasumatsu <th.yasumatsu@gmail.com>

    [ Upstream commit 30e29a9a2bc6a4888335a6ede968b75cd329657a ]

    In prealloc_elems_and_freelist(), the multiplication to calculate the
    size passed to bpf_map_area_alloc() could lead to an integer overflow.
    As a result, out-of-bounds write could occur in pcpu_freelist_populate()
    as reported by KASAN:

    [...]
    [ 16.968613] BUG: KASAN: slab-out-of-bounds in pcpu_freelist_populate+0xd9/0x100
    [ 16.969408] Write of size 8 at addr ffff888104fc6ea0 by task crash/78
    [ 16.970038]
    [ 16.970195] CPU: 0 PID: 78 Comm: crash Not tainted 5.15.0-rc2+ #1
    [ 16.970878] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014
    [ 16.972026] Call Trace:
    [ 16.972306] dump_stack_lvl+0x34/0x44
    [ 16.972687] print_address_description.constprop.0+0x21/0x140
    [ 16.973297] ? pcpu_freelist_populate+0xd9/0x100
    [ 16.973777] ? pcpu_freelist_populate+0xd9/0x100
    [ 16.974257] kasan_report.cold+0x7f/0x11b
    [ 16.974681] ? pcpu_freelist_populate+0xd9/0x100
    [ 16.975190] pcpu_freelist_populate+0xd9/0x100
    [ 16.975669] stack_map_alloc+0x209/0x2a0
    [ 16.976106] __sys_bpf+0xd83/0x2ce0
    [...]

    The possibility of this overflow was originally discussed in [0], but
    was overlooked.

    Fix the integer overflow by changing elem_size to u64 from u32.

    [0] https://lore.kernel.org/bpf/728b238e-a481-eb50-98e9-b0f430ab01e7@gmail.com/

    Fixes: 557c0c6e7df8 ("bpf: convert stackmap to pre-allocation")
    Signed-off-by: Tatsuhiko Yasumatsu <th.yasumatsu@gmail.com>
    Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
    Link: https://lore.kernel.org/bpf/20210930135545.173698-1-th.yasumatsu@gmail.com
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    kernel/bpf/stackmap.c | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
    index ebf60848d5eb..4477873ac3a0 100644
    --- a/kernel/bpf/stackmap.c
    +++ b/kernel/bpf/stackmap.c
    @@ -64,7 +64,8 @@ static inline int stack_map_data_size(struct bpf_map *map)

    static int prealloc_elems_and_freelist(struct bpf_stack_map *smap)
    {
    - u32 elem_size = sizeof(struct stack_map_bucket) + smap->map.value_size;
    + u64 elem_size = sizeof(struct stack_map_bucket) +
    + (u64)smap->map.value_size;
    int err;

    smap->elems = bpf_map_area_alloc(elem_size * smap->map.max_entries,
    --
    2.33.0


    \
     
     \ /
      Last update: 2021-10-11 16:07    [W:2.491 / U:0.148 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site