Kdump kernel fails to load because of crash on mount of overlayfs: BUG: unable to handle kernel NULL pointer dereference at 0000000000000060 .... Call Trace: seq_path+0x64/0xb0 print_paths_option+0x79/0xa0 ovl_show_options+0x3a/0x320 show_mountinfo+0x1ee/0x290 seq_read+0x2f8/0x400 vfs_read+0x9d/0x150 ksys_read+0x4f/0xb0 do_syscall_64+0x5b/0x1a0
This is cause by OOB access of ofs->lowerpaths. We transfer to print_paths_option() ofs->numlayer as size of ->lowerpaths array, but it's not. The correct number of lowerpaths elements is ->numlower in 'struct ovl_entry'. So move lowerpaths there and use oe->numlower as array size. Fixes: 17fc61697f73 ("overlayfs: add dynamic path resolving in mount options") Fixes: 2191d729083d ("overlayfs: add mnt_id paths options") https://jira.sw.ru/browse/PSBM-123508 Signed-off-by: Andrey Ryabinin <aryabi...@virtuozzo.com> --- fs/overlayfs/ovl_entry.h | 2 +- fs/overlayfs/super.c | 37 ++++++++++++++++++++----------------- 2 files changed, 21 insertions(+), 18 deletions(-) diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h index ea1906448ec5..2315089a0211 100644 --- a/fs/overlayfs/ovl_entry.h +++ b/fs/overlayfs/ovl_entry.h @@ -54,7 +54,6 @@ struct ovl_fs { unsigned int numlayer; /* Number of unique fs among layers including upper fs */ unsigned int numfs; - struct path *lowerpaths; const struct ovl_layer *layers; struct ovl_sb *fs; /* workbasepath is the path at workdir= mount option */ @@ -98,6 +97,7 @@ struct ovl_entry { struct rcu_head rcu; }; unsigned numlower; + struct path *lowerpaths; struct ovl_path lowerstack[]; }; diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c index 3755f280036f..fb419617564c 100644 --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -70,8 +70,12 @@ static void ovl_entry_stack_free(struct ovl_entry *oe) { unsigned int i; - for (i = 0; i < oe->numlower; i++) + for (i = 0; i < oe->numlower; i++) { dput(oe->lowerstack[i].dentry); + if (oe->lowerpaths) + path_put(&oe->lowerpaths[i]); + } + kfree(oe->lowerpaths); } static bool ovl_metacopy_def = IS_ENABLED(CONFIG_OVERLAY_FS_METACOPY); @@ -241,11 +245,6 @@ static void ovl_free_fs(struct ovl_fs *ofs) ovl_inuse_unlock(ofs->upper_mnt->mnt_root); mntput(ofs->upper_mnt); path_put(&ofs->upperpath); - if (ofs->lowerpaths) { - for (i = 0; i < ofs->numlayer; i++) - path_put(&ofs->lowerpaths[i]); - kfree(ofs->lowerpaths); - } for (i = 1; i < ofs->numlayer; i++) { iput(ofs->layers[i].trap); mntput(ofs->layers[i].mnt); @@ -359,9 +358,10 @@ static int ovl_show_options(struct seq_file *m, struct dentry *dentry) { struct super_block *sb = dentry->d_sb; struct ovl_fs *ofs = sb->s_fs_info; + struct ovl_entry *oe = OVL_E(dentry); if (ovl_dyn_path_opts) { - print_paths_option(m, "lowerdir", ofs->lowerpaths, ofs->numlayer); + print_paths_option(m, "lowerdir", oe->lowerpaths, oe->numlower); if (ofs->config.upperdir) { print_path_option(m, "upperdir", &ofs->upperpath); print_path_option(m, "workdir", &ofs->workbasepath); @@ -375,7 +375,7 @@ static int ovl_show_options(struct seq_file *m, struct dentry *dentry) } if (ovl_mnt_id_path_opts) { - print_mnt_ids_option(m, "lowerdir_mnt_id", ofs->lowerpaths, ofs->numlayer); + print_mnt_ids_option(m, "lowerdir_mnt_id", oe->lowerpaths, oe->numlower); /* * We don't need to show mnt_id for workdir because it * on the same mount as upperdir. @@ -1626,6 +1626,7 @@ static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb, int err; char *lowertmp, *lower; unsigned int stacklen, numlower = 0, i; + struct path *stack = NULL; struct ovl_entry *oe; err = -ENOMEM; @@ -1649,14 +1650,14 @@ static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb, } err = -ENOMEM; - ofs->lowerpaths = kcalloc(stacklen, sizeof(struct path), GFP_KERNEL); - if (!ofs->lowerpaths) + stack = kcalloc(stacklen, sizeof(struct path), GFP_KERNEL); + if (!stack) goto out_err; err = -EINVAL; lower = lowertmp; for (numlower = 0; numlower < stacklen; numlower++) { - err = ovl_lower_dir(lower, &ofs->lowerpaths[numlower], ofs, + err = ovl_lower_dir(lower, &stack[numlower], ofs, &sb->s_stack_depth); if (err) goto out_err; @@ -1671,7 +1672,7 @@ static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb, goto out_err; } - err = ovl_get_layers(sb, ofs, ofs->lowerpaths, numlower); + err = ovl_get_layers(sb, ofs, stack, numlower); if (err) goto out_err; @@ -1681,9 +1682,10 @@ static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb, goto out_err; for (i = 0; i < numlower; i++) { - oe->lowerstack[i].dentry = dget(ofs->lowerpaths[i].dentry); + oe->lowerstack[i].dentry = dget(stack[i].dentry); oe->lowerstack[i].layer = &ofs->layers[i+1]; } + oe->lowerpaths = stack; out: kfree(lowertmp); @@ -1691,10 +1693,11 @@ static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb, return oe; out_err: - for (i = 0; i < numlower; i++) - path_put_init(&ofs->lowerpaths[i]); - kfree(ofs->lowerpaths); - ofs->lowerpaths = NULL; + if (stack) { + for (i = 0; i < numlower; i++) + path_put(&stack[i]); + kfree(stack); + } oe = ERR_PTR(err); goto out; } -- 2.26.2 _______________________________________________ Devel mailing list Devel@openvz.org https://lists.openvz.org/mailman/listinfo/devel