5.4-stable review patch. If anyone has any objections, please let me know.
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From: Liam Howlett liam.howlett@oracle.com
commit f829b4b212a315b912cb23fd10aaf30534bb5ce9 upstream.
When the superuser flushes the entire cache, the mmap_read_lock() is not taken, but mmap_read_unlock() is called. Add the missing mmap_read_lock() call.
Fixes: cd2567b6850b1648 ("m68k: call find_vma with the mmap_sem held in sys_cacheflush()") Signed-off-by: Liam R. Howlett Liam.Howlett@Oracle.com Reviewed-by: Matthew Wilcox (Oracle) willy@infradead.org Link: https://lore.kernel.org/r/20210407200032.764445-1-Liam.Howlett@Oracle.com Signed-off-by: Geert Uytterhoeven geert@linux-m68k.org [ mmap_read_lock() open-coded using down_read() as was done prior to v5.8 ] Signed-off-by: Finn Thain fthain@linux-m68k.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/m68k/kernel/sys_m68k.c | 2 ++ 1 file changed, 2 insertions(+)
--- a/arch/m68k/kernel/sys_m68k.c +++ b/arch/m68k/kernel/sys_m68k.c @@ -388,6 +388,8 @@ sys_cacheflush (unsigned long addr, int ret = -EPERM; if (!capable(CAP_SYS_ADMIN)) goto out; + + down_read(¤t->mm->mmap_sem); } else { struct vm_area_struct *vma;