Messages in this thread | | | Date | Sat, 16 Mar 2013 14:33:57 -0400 | From | Sasha Levin <> | Subject | Re: use after free in sysfs_find_dirent |
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On 03/16/2013 11:58 AM, Ming Lei wrote: > On Sat, Mar 16, 2013 at 11:22 PM, Ming Lei <tom.leiming@gmail.com> wrote: >> On Sat, Mar 16, 2013 at 11:07 PM, Sasha Levin <levinsasha928@gmail.com> wrote: >>> >>> Hi Ming, >>> >>> With your patch: >>> >>> >>> [ 1525.874312] release_sysfs_dirent sysfs_dirent use after free: ptysb-uevent >> >> Sasha, thanks for your test. >> >> So is the oops always triggered on this node of 'ptysb-uevent' or the node name >> is changed every time? > > Also, we may dump stack on the release path with the below patch to see who > did the ugly free. > > -- > diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c > index 2fbdff6..993671d 100644 > --- a/fs/sysfs/dir.c > +++ b/fs/sysfs/dir.c > @@ -281,6 +281,12 @@ void release_sysfs_dirent(struct sysfs_dirent * sd) > */ > parent_sd = sd->s_parent; > > + if(!(sd->s_flags & SYSFS_FLAG_REMOVED)) { > + printk("%s sysfs_dirent use after free: %s-%s\n", > + __func__, parent_sd->s_name, sd->s_name); > + dump_stack(); > + } > + > if (sysfs_type(sd) == SYSFS_KOBJ_LINK) > sysfs_put(sd->s_symlink.target_sd); > if (sysfs_type(sd) & SYSFS_COPY_NAME) > @@ -962,6 +968,9 @@ static struct sysfs_dirent *sysfs_dir_pos(const void *ns, > int valid = !(pos->s_flags & SYSFS_FLAG_REMOVED) && > pos->s_parent == parent_sd && > hash == pos->s_hash; > + if (valid && (atomic_read(&pos->s_count) <= 1)) > + printk("%s sysfs_dirent use after free: %s-%s\n", > + __func__, parent_sd->s_name, pos->s_name); > sysfs_put(pos); > if (!valid) > pos = NULL; >
I don't think it shows what we want it to show thought:
[ 327.416905] Pid: 10504, comm: trinity-child98 Tainted: G W 3.9.0-rc2-next-20130315-sasha-00046-gecde602-dirty #301 [ 327.418815] Call Trace: [ 327.419255] [<ffffffff812f880e>] release_sysfs_dirent+0x4e/0x120 [ 327.420595] [<ffffffff812f89d2>] sysfs_dir_pos+0x92/0x130 [ 327.421608] [<ffffffff812f8b8d>] sysfs_readdir+0x11d/0x280 [ 327.422562] [<ffffffff8128b070>] ? SyS_ioctl+0xa0/0xa0 [ 327.423441] [<ffffffff8128b070>] ? SyS_ioctl+0xa0/0xa0 [ 327.424314] [<ffffffff8128b3e8>] vfs_readdir+0x78/0xc0 [ 327.425263] [<ffffffff8128b54c>] SyS_getdents+0x8c/0x110 [ 327.426173] [<ffffffff83d919d8>] tracesys+0xe1/0xe6
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