2a855dd01b
All architectures in the kernel increment/decrement the stack pointer before storing values on the stack. On architectures which have the stack grow down sas_ss_sp == sp is not on the alternate signal stack while sas_ss_sp + sas_ss_size == sp is on the alternate signal stack. On architectures which have the stack grow up sas_ss_sp == sp is on the alternate signal stack while sas_ss_sp + sas_ss_size == sp is not on the alternate signal stack. The current implementation fails for architectures which have the stack grow down on the corner case where sas_ss_sp == sp.This was reported as Debian bug #544905 on AMD64. Simplified test case: http://download.breakpoint.cc/tc-sig-stack.c The test case creates the following stack scenario: 0xn0300 stack top 0xn0200 alt stack pointer top (when switching to alt stack) 0xn01ff alt stack end 0xn0100 alt stack start == stack pointer If the signal is sent the stack pointer is pointing to the base address of the alt stack and the kernel erroneously decides that it has already switched to the alternate stack because of the current check for "sp - sas_ss_sp < sas_ss_size" On parisc (stack grows up) the scenario would be: 0xn0200 stack pointer 0xn01ff alt stack end 0xn0100 alt stack start = alt stack pointer base (when switching to alt stack) 0xn0000 stack base This is handled correctly by the current implementation. [ tglx: Modified for archs which have the stack grow up (parisc) which would fail with the correct implementation for stack grows down. Added a check for sp >= current->sas_ss_sp which is strictly not necessary but makes the code symetric for both variants ] Signed-off-by: Sebastian Andrzej Siewior <sebastian@breakpoint.cc> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com> Cc: Kyle McMartin <kyle@mcmartin.ca> Cc: stable@kernel.org LKML-Reference: <20091025143758.GA6653@Chamillionaire.breakpoint.cc> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> |
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| acpi | ||
| asm-generic | ||
| crypto | ||
| drm | ||
| keys | ||
| linux | ||
| math-emu | ||
| media | ||
| mtd | ||
| net | ||
| pcmcia | ||
| rdma | ||
| rxrpc | ||
| scsi | ||
| sound | ||
| trace | ||
| video | ||
| xen | ||
| Kbuild | ||