[4.19.y-cip] m68k: Add missing mmap_read_lock() to sys_cacheflush()

Commit Message

Finn Thain Feb. 13, 2025, 7:24 a.m. UTC

From: Liam Howlett <[e-mail]>

[ Upstream commit f829b4b212a315b912cb23fd10aaf30534bb5ce9 ]

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 <[e-mail]>
Reviewed-by: Matthew Wilcox (Oracle) <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Geert Uytterhoeven <[e-mail]>
[ mmap_read_lock() open-coded using down_read() as was done prior to v5.8 ]
Signed-off-by: Finn Thain <[e-mail]>
---
 arch/m68k/kernel/sys_m68k.c | 2 ++
 1 file changed, 2 insertions(+)

Patch

diff --git a/arch/m68k/kernel/sys_m68k.c b/arch/m68k/kernel/sys_m68k.c
index 6363ec83a290..38dcc1a2097d 100644
--- a/arch/m68k/kernel/sys_m68k.c
+++ b/arch/m68k/kernel/sys_m68k.c
@@ -388,6 +388,8 @@  sys_cacheflush (unsigned long addr, int scope, int cache, unsigned long len)
 		ret = -EPERM;
 		if (!capable(CAP_SYS_ADMIN))
 			goto out;
+
+		down_read(&current->mm->mmap_sem);
 	} else {
 		struct vm_area_struct *vma;