diff options
| author | Andy Lutomirski <luto@kernel.org> | 2019-11-20 11:49:33 +0300 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2019-11-21 21:37:43 +0300 |
| commit | 4c4fd55d3d59a41ddfa6ecba7e76928921759f43 (patch) | |
| tree | 6ba323bbb4d8e772ecb6679ce73b0d0260f8fcfe /arch/x86/entry | |
| parent | 40ad2199580e248dce2a2ebb722854180c334b9e (diff) | |
| download | linux-4c4fd55d3d59a41ddfa6ecba7e76928921759f43.tar.xz | |
x86/entry/32: Use %ss segment where required
When re-building the IRET frame we use %eax as an destination %esp,
make sure to then also match the segment for when there is a nonzero
SS base (ESPFIX).
[peterz: Changelog and minor edits]
Fixes: 3c88c692c287 ("x86/stackframe/32: Provide consistent pt_regs")
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@kernel.org
Diffstat (limited to 'arch/x86/entry')
| -rw-r--r-- | arch/x86/entry/entry_32.S | 19 |
1 files changed, 14 insertions, 5 deletions
diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S index f4335ac9692f..341597ecdcb5 100644 --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -210,6 +210,8 @@ /* * The high bits of the CS dword (__csh) are used for CS_FROM_*. * Clear them in case hardware didn't do this for us. + * + * Be careful: we may have nonzero SS base due to ESPFIX. */ andl $0x0000ffff, 3*4(%esp) @@ -263,6 +265,13 @@ .endm .macro IRET_FRAME + /* + * We're called with %ds, %es, %fs, and %gs from the interrupted + * frame, so we shouldn't use them. Also, we may be in ESPFIX + * mode and therefore have a nonzero SS base and an offset ESP, + * so any attempt to access the stack needs to use SS. (except for + * accesses through %esp, which automatically use SS.) + */ testl $CS_FROM_KERNEL, 1*4(%esp) jz .Lfinished_frame_\@ @@ -276,20 +285,20 @@ movl 5*4(%esp), %eax # (modified) regs->sp movl 4*4(%esp), %ecx # flags - movl %ecx, -4(%eax) + movl %ecx, %ss:-1*4(%eax) movl 3*4(%esp), %ecx # cs andl $0x0000ffff, %ecx - movl %ecx, -8(%eax) + movl %ecx, %ss:-2*4(%eax) movl 2*4(%esp), %ecx # ip - movl %ecx, -12(%eax) + movl %ecx, %ss:-3*4(%eax) movl 1*4(%esp), %ecx # eax - movl %ecx, -16(%eax) + movl %ecx, %ss:-4*4(%eax) popl %ecx - lea -16(%eax), %esp + lea -4*4(%eax), %esp popl %eax .Lfinished_frame_\@: .endm |