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authorCharan Teja Kalla <charante@codeaurora.org>2020-06-19 14:57:19 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2020-07-29 11:18:29 +0300
commit722c6e954c90eca93ac89980e7b79577cd141777 (patch)
tree726e5e4888db28732d67a6e5282719460054c667 /drivers/dma-buf/dma-buf.c
parent44838b9563049af7558b6cac25d30086f3c15603 (diff)
downloadlinux-722c6e954c90eca93ac89980e7b79577cd141777.tar.xz
dmabuf: use spinlock to access dmabuf->name
[ Upstream commit 6348dd291e3653534a9e28e6917569bc9967b35b ] There exists a sleep-while-atomic bug while accessing the dmabuf->name under mutex in the dmabuffs_dname(). This is caused from the SELinux permissions checks on a process where it tries to validate the inherited files from fork() by traversing them through iterate_fd() (which traverse files under spin_lock) and call match_file(security/selinux/hooks.c) where the permission checks happen. This audit information is logged using dump_common_audit_data() where it calls d_path() to get the file path name. If the file check happen on the dmabuf's fd, then it ends up in ->dmabuffs_dname() and use mutex to access dmabuf->name. The flow will be like below: flush_unauthorized_files() iterate_fd() spin_lock() --> Start of the atomic section. match_file() file_has_perm() avc_has_perm() avc_audit() slow_avc_audit() common_lsm_audit() dump_common_audit_data() audit_log_d_path() d_path() dmabuffs_dname() mutex_lock()--> Sleep while atomic. Call trace captured (on 4.19 kernels) is below: ___might_sleep+0x204/0x208 __might_sleep+0x50/0x88 __mutex_lock_common+0x5c/0x1068 __mutex_lock_common+0x5c/0x1068 mutex_lock_nested+0x40/0x50 dmabuffs_dname+0xa0/0x170 d_path+0x84/0x290 audit_log_d_path+0x74/0x130 common_lsm_audit+0x334/0x6e8 slow_avc_audit+0xb8/0xf8 avc_has_perm+0x154/0x218 file_has_perm+0x70/0x180 match_file+0x60/0x78 iterate_fd+0x128/0x168 selinux_bprm_committing_creds+0x178/0x248 security_bprm_committing_creds+0x30/0x48 install_exec_creds+0x1c/0x68 load_elf_binary+0x3a4/0x14e0 search_binary_handler+0xb0/0x1e0 So, use spinlock to access dmabuf->name to avoid sleep-while-atomic. Cc: <stable@vger.kernel.org> [5.3+] Signed-off-by: Charan Teja Kalla <charante@codeaurora.org> Reviewed-by: Michael J. Ruhl <michael.j.ruhl@intel.com> Acked-by: Christian König <christian.koenig@amd.com> [sumits: added comment to spinlock_t definition to avoid warning] Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org> Link: https://patchwork.freedesktop.org/patch/msgid/a83e7f0d-4e54-9848-4b58-e1acdbe06735@codeaurora.org Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'drivers/dma-buf/dma-buf.c')
-rw-r--r--drivers/dma-buf/dma-buf.c11
1 files changed, 7 insertions, 4 deletions
diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index cf65a47310c3..eba7e3fe769c 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -45,10 +45,10 @@ static char *dmabuffs_dname(struct dentry *dentry, char *buffer, int buflen)
size_t ret = 0;
dmabuf = dentry->d_fsdata;
- mutex_lock(&dmabuf->lock);
+ spin_lock(&dmabuf->name_lock);
if (dmabuf->name)
ret = strlcpy(name, dmabuf->name, DMA_BUF_NAME_LEN);
- mutex_unlock(&dmabuf->lock);
+ spin_unlock(&dmabuf->name_lock);
return dynamic_dname(dentry, buffer, buflen, "/%s:%s",
dentry->d_name.name, ret > 0 ? name : "");
@@ -338,8 +338,10 @@ static long dma_buf_set_name(struct dma_buf *dmabuf, const char __user *buf)
kfree(name);
goto out_unlock;
}
+ spin_lock(&dmabuf->name_lock);
kfree(dmabuf->name);
dmabuf->name = name;
+ spin_unlock(&dmabuf->name_lock);
out_unlock:
mutex_unlock(&dmabuf->lock);
@@ -402,10 +404,10 @@ static void dma_buf_show_fdinfo(struct seq_file *m, struct file *file)
/* Don't count the temporary reference taken inside procfs seq_show */
seq_printf(m, "count:\t%ld\n", file_count(dmabuf->file) - 1);
seq_printf(m, "exp_name:\t%s\n", dmabuf->exp_name);
- mutex_lock(&dmabuf->lock);
+ spin_lock(&dmabuf->name_lock);
if (dmabuf->name)
seq_printf(m, "name:\t%s\n", dmabuf->name);
- mutex_unlock(&dmabuf->lock);
+ spin_unlock(&dmabuf->name_lock);
}
static const struct file_operations dma_buf_fops = {
@@ -537,6 +539,7 @@ struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info)
dmabuf->size = exp_info->size;
dmabuf->exp_name = exp_info->exp_name;
dmabuf->owner = exp_info->owner;
+ spin_lock_init(&dmabuf->name_lock);
init_waitqueue_head(&dmabuf->poll);
dmabuf->cb_excl.poll = dmabuf->cb_shared.poll = &dmabuf->poll;
dmabuf->cb_excl.active = dmabuf->cb_shared.active = 0;