mirror of https://github.com/torvalds/linux.git
3 Commits
| Author | SHA1 | Message | Date |
|---|---|---|---|
Carlos Llamas
|
3ebcd3460c |
binder: fix double-free in dbitmap
A process might fail to allocate a new bitmap when trying to expand its
proc->dmap. In that case, dbitmap_grow() fails and frees the old bitmap
via dbitmap_free(). However, the driver calls dbitmap_free() again when
the same process terminates, leading to a double-free error:
==================================================================
BUG: KASAN: double-free in binder_proc_dec_tmpref+0x2e0/0x55c
Free of addr ffff00000b7c1420 by task kworker/9:1/209
CPU: 9 UID: 0 PID: 209 Comm: kworker/9:1 Not tainted 6.17.0-rc6-dirty #5 PREEMPT
Hardware name: linux,dummy-virt (DT)
Workqueue: events binder_deferred_func
Call trace:
kfree+0x164/0x31c
binder_proc_dec_tmpref+0x2e0/0x55c
binder_deferred_func+0xc24/0x1120
process_one_work+0x520/0xba4
[...]
Allocated by task 448:
__kmalloc_noprof+0x178/0x3c0
bitmap_zalloc+0x24/0x30
binder_open+0x14c/0xc10
[...]
Freed by task 449:
kfree+0x184/0x31c
binder_inc_ref_for_node+0xb44/0xe44
binder_transaction+0x29b4/0x7fbc
binder_thread_write+0x1708/0x442c
binder_ioctl+0x1b50/0x2900
[...]
==================================================================
Fix this issue by marking proc->map NULL in dbitmap_free().
Cc: stable@vger.kernel.org
Fixes:
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Carlos Llamas
|
11512c197d |
binder: fix descriptor lookup for context manager
In commit |
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Carlos Llamas
|
15d9da3f81 |
binder: use bitmap for faster descriptor lookup
When creating new binder references, the driver assigns a descriptor id that is shared with userspace. Regrettably, the driver needs to keep the descriptors small enough to accommodate userspace potentially using them as Vector indexes. Currently, the driver performs a linear search on the rb-tree of references to find the smallest available descriptor id. This approach, however, scales poorly as the number of references grows. This patch introduces the usage of bitmaps to boost the performance of descriptor assignments. This optimization results in notable performance gains, particularly in processes with a large number of references. The following benchmark with 100,000 references showcases the difference in latency between the dbitmap implementation and the legacy approach: [ 587.145098] get_ref_desc_olocked: 15us (dbitmap on) [ 602.788623] get_ref_desc_olocked: 47343us (dbitmap off) Note the bitmap size is dynamically adjusted in line with the number of references, ensuring efficient memory usage. In cases where growing the bitmap is not possible, the driver falls back to the slow legacy method. A previous attempt to solve this issue was proposed in [1]. However, such method involved adding new ioctls which isn't great, plus older userspace code would not have benefited from the optimizations either. Link: https://lore.kernel.org/all/20240417191418.1341988-1-cmllamas@google.com/ [1] Cc: Tim Murray <timmurray@google.com> Cc: Arve Hjønnevåg <arve@android.com> Cc: Alice Ryhl <aliceryhl@google.com> Cc: Martijn Coenen <maco@android.com> Cc: Todd Kjos <tkjos@android.com> Cc: John Stultz <jstultz@google.com> Cc: Steven Moreland <smoreland@google.com> Suggested-by: Nick Chen <chenjia3@oppo.com> Reviewed-by: Alice Ryhl <aliceryhl@google.com> Signed-off-by: Carlos Llamas <cmllamas@google.com> Link: https://lore.kernel.org/r/20240612042535.1556708-1-cmllamas@google.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |