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locking/refcount: Move saturation warnings out of line

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[ Upstream commit 1eb085d94256aaa69b00cf5a86e3c5f5bb2bc460 ]

Having the refcount saturation and warnings inline bloats the text,
despite the fact that these paths should never be executed in normal
operation.

Move the refcount saturation and warnings out of line to reduce the
image size when refcount_t checking is enabled. Relative to an x86_64
defconfig, the sizes reported by bloat-o-meter are:

 # defconfig+REFCOUNT_FULL, inline saturation (i.e. before this patch)
 Total: Before=14762076, After=14915442, chg +1.04%

 # defconfig+REFCOUNT_FULL, out-of-line saturation (i.e. after this patch)
 Total: Before=14762076, After=14835497, chg +0.50%

A side-effect of this change is that we now only get one warning per
refcount saturation type, rather than one per problematic call-site.

Signed-off-by: Will Deacon <[email protected]>
Reviewed-by: Ard Biesheuvel <[email protected]>
Reviewed-by: Kees Cook <[email protected]>
Tested-by: Hanjun Guo <[email protected]>
Cc: Ard Biesheuvel <[email protected]>
Cc: Elena Reshetova <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>
This commit is contained in:
Will Deacon 2019-11-21 11:58:58 +00:00 • committed by Greg Kroah-Hartman
commit 0d3182fbe6
2 changed files with 48 additions and 19 deletions
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28
lib/refcount.c
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@ -8,6 +8,34 @@
#include <linux/spinlock.h>
#include <linux/bug.h>
#define REFCOUNT_WARN(str) WARN_ONCE(1, "refcount_t: " str ".\n")
void refcount_warn_saturate(refcount_t *r, enum refcount_saturation_type t)
{
refcount_set(r, REFCOUNT_SATURATED);
switch (t) {
case REFCOUNT_ADD_NOT_ZERO_OVF:
REFCOUNT_WARN("saturated; leaking memory");
break;
case REFCOUNT_ADD_OVF:
REFCOUNT_WARN("saturated; leaking memory");
break;
case REFCOUNT_ADD_UAF:
REFCOUNT_WARN("addition on 0; use-after-free");
break;
case REFCOUNT_SUB_UAF:
REFCOUNT_WARN("underflow; use-after-free");
break;
case REFCOUNT_DEC_LEAK:
REFCOUNT_WARN("decrement hit 0; leaking memory");
break;
default:
REFCOUNT_WARN("unknown saturation event!?");
}
}
EXPORT_SYMBOL(refcount_warn_saturate);
/**
* refcount_dec_if_one - decrement a refcount if it is 1
* @r: the refcount