Charan Teja Kalla 6348dd291e dmabuf: use spinlock to access dmabuf->name ... 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		2020-07-10 15:39:29 +05:30
..
heaps
dma-buf.c	dmabuf: use spinlock to access dmabuf->name	2020-07-10 15:39:29 +05:30
dma-fence-array.c
dma-fence-chain.c
dma-fence.c	dma-buf: Use atomic_fetch_add() for the context id	2020-05-13 13:38:59 +01:00
dma-heap.c
dma-resv.c	DMA reservations: use the new mmap locking API	2020-06-09 09:39:14 -07:00
Kconfig	treewide: replace '---help---' in Kconfig files with 'help'	2020-06-14 01:57:21 +09:00
Makefile
selftest.c
selftest.h
selftests.h
seqno-fence.c
st-dma-fence-chain.c
st-dma-fence.c
sw_sync.c
sync_debug.c
sync_debug.h
sync_file.c
sync_trace.h
udmabuf.c