Although it is very unlikely that the allocation during init would fail any such failure should point to the original cause to allow easier understanding of the ensuing null-pointer dereference splat.
Signed-off-by: Nicholas Mc Guire <hof...@osadl.org> --- Problem located with experimental coccinelle script V2: Russell King <li...@armlinux.org.uk> pointed out that the use of WARN_ON() would result in a stack trace followed by the oops due to dereferencing of the NULL pointer and so make it even less likely that users would uncover the actual cause - so drop the WARN_ON() and use a short pr_err() message that points to the oops cause directly. Note that this will trigger a checkpatch WARNING "WARNING: Possible unnecessary 'out of memory' message" but comparing the oops with an without the one-line pr_err I would argue that it makes sense to include it: <snip> [ 8061.514840] shared page allocation failure in hello_init() [ 8113.563239] BUG: unable to handle kernel NULL pointer dereference at 0000000000000000 [ 8113.563250] #PF error: [WRITE] [ 8113.563255] PGD 8000000129993067 P4D 8000000129993067 PUD 129992067 PMD 0 [ 8113.563267] Oops: 0002 [#1] SMP PTI [ 8113.563276] CPU: 2 PID: 2656 Comm: bash Tainted: G W O 5.0.0-rc3livepatchtest-next-20190123+ #4 [ 8113.563280] Hardware name: Quanta TWH/TWH, BIOS QU221 10/14/2011 [ 8113.563292] RIP: 0010:foo_store+0x3a/0x90 [hello_chardev] ... <snip> Patch was compile-tested: mvebu_v7_defconfig (implies MACH_MVEBU_ANY=y) (with some unrelated sparse warnings about missing syscalls) Patch is against 5.1-rc4 (localversion-next is 20190415) arch/arm/mach-mvebu/board-v7.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/arm/mach-mvebu/board-v7.c b/arch/arm/mach-mvebu/board-v7.c index 0b10acd..df84cb6 100644 --- a/arch/arm/mach-mvebu/board-v7.c +++ b/arch/arm/mach-mvebu/board-v7.c @@ -128,6 +128,9 @@ static void __init i2c_quirk(void) struct property *new_compat; new_compat = kzalloc(sizeof(*new_compat), GFP_KERNEL); + if (!new_compat) + pr_err("new_compat allocation failure in %s()\n", + __func__); new_compat->name = kstrdup("compatible", GFP_KERNEL); new_compat->length = sizeof("marvell,mv78230-a0-i2c"); -- 2.1.4