Messages in this thread Patch in this message | | | Date | Thu, 20 Apr 2006 21:39:13 -0700 | From | Greg KH <> | Subject | [patch 13/22] x86: dont allow tail-calls in sys_ftruncate() |
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From: Linus Torvalds <torvalds@osdl.org>
x86: don't allow tail-calls in sys_ftruncate[64]()
Gcc thinks it owns the incoming argument stack, but that's not true for "asmlinkage" functions, and it corrupts the caller-set-up argument stack when it pushes the third argument onto the stack. Which can result in %ebx getting corrupted in user space.
Now, normally nobody sane would ever notice, since libc will save and restore %ebx anyway over the system call, but it's still wrong.
I'd much rather have "asmlinkage" tell gcc directly that it doesn't own the stack, but no such attribute exists, so we're stuck with our hacky manual "prevent_tail_call()" macro once more (we've had the same issue before with sys_waitpid() and sys_wait4()).
Thanks to Hans-Werner Hilse <hilse@sub.uni-goettingen.de> for reporting the issue and testing the fix.
Signed-off-by: Linus Torvalds <torvalds@osdl.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- fs/open.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)
--- linux-2.6.16.9.orig/fs/open.c +++ linux-2.6.16.9/fs/open.c @@ -330,7 +330,9 @@ out: asmlinkage long sys_ftruncate(unsigned int fd, unsigned long length) { - return do_sys_ftruncate(fd, length, 1); + long ret = do_sys_ftruncate(fd, length, 1); + prevent_tail_call(ret); + return ret; } /* LFS versions of truncate are only needed on 32 bit machines */ @@ -342,7 +344,9 @@ asmlinkage long sys_truncate64(const cha asmlinkage long sys_ftruncate64(unsigned int fd, loff_t length) { - return do_sys_ftruncate(fd, length, 0); + long ret = do_sys_ftruncate(fd, length, 0); + prevent_tail_call(ret); + return ret; } #endif -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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