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mm: always expand the stack with the mmap write lock held

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This finishes the job of always holding the mmap write lock when
extending the user stack vma, and removes the 'write_locked' argument
from the vm helper functions again.

For some cases, we just avoid expanding the stack at all: drivers and
page pinning really shouldn't be extending any stacks.  Let's see if any
strange users really wanted that.

It's worth noting that architectures that weren't converted to the new
lock_mm_and_find_vma() helper function are left using the legacy
"expand_stack()" function, but it has been changed to drop the mmap_lock
and take it for writing while expanding the vma.  This makes it fairly
straightforward to convert the remaining architectures.

As a result of dropping and re-taking the lock, the calling conventions
for this function have also changed, since the old vma may no longer be
valid.  So it will now return the new vma if successful, and NULL - and
the lock dropped - if the area could not be extended.

Tested-by: Vegard Nossum <vegard.nossum@oracle.com>
Tested-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de> # ia64
Tested-by: Frank Scheiner <frank.scheiner@web.de> # ia64
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Linus Torvalds 2023-06-24 13:45:51 -07:00
parent f313c51d26
commit 8d7071af89
17 changed files with 169 additions and 116 deletions
Download patch file Download diff file Expand all files Collapse all files

9
arch/m68k/mm/fault.c
View file

@ -105,8 +105,9 @@ retry:
if (address + 256 < rdusp())
goto map_err;
}
if (expand_stack(vma, address))
goto map_err;
vma = expand_stack(mm, address);
if (!vma)
goto map_err_nosemaphore;
/*
* Ok, we have a good vm_area for this memory access, so
@ -196,10 +197,12 @@ bus_err:
goto send_sig;
map_err:
mmap_read_unlock(mm);
map_err_nosemaphore:
current->thread.signo = SIGSEGV;
current->thread.code = SEGV_MAPERR;
current->thread.faddr = address;
goto send_sig;
return send_fault_sig(regs);
acc_err:
current->thread.signo = SIGSEGV;